Issue title:  undefined is not a function
 Issue body: Hi

I'm getting an error on a new install, from what I can tell I have everything installed ok. Do you know what would cause this?

Here is the error

```
TypeError: undefined is not a function
    at http://dev.rvwd.com/js/angular-redactor.js:36:32
    at http://ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.min.js:113:78
    at e (http://ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.min.js:33:287)
    at http://ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.min.js:37:1 
```

It seems to be this line

```
$timeout(function () {
        editor = $_element.redactor(options);
        ngModel.$render();
      });
```

 Comments: 
 Comment 0: I just tried again with your demo after installing angular and redactor via bower and I received the same error

 Comment 1: What version of redactor are you using?

 Comment 2: I'm going to close this, unless there is a known bug.

 Comment 3: Why did you close this @TylerGarlick? I'm getting the same error.

If I change line 43 from...

```
editor = $_element.redactor(options);
```

to 

```
editor = $('textarea').redactor(options);
```

...I don't receive the error. Obviously this makes the directive pointless, but I'm just trying to show that there seems to be a bug.

 Comment 4: I'll take a look into it, sorry I thought you all resolved it.

 Comment 5: No worries. I actually just jumped on this issue because I was getting the same error. 

Thanks for looking into it. 

 Comment 6: What version of redactor are you all using?

 Comment 7: I'm using 8.2.2. I wanted to try it out before buying it and that's the version available in bower. 

If I use the version from Redactor's example pages (`http://imperavi.com/js/redactor/redactor.js`), I get the same error

 Comment 8: It looks like someone else was having the same issue in https://github.com/TylerGarlick/angular-redactor/issues/7. 

If I change `$_element` to `$($_element)`, it works fine. Perhaps something in `angular.element` changed, which is what broke it again. I'm using Angular v1.3.0-build.3001+sha.d2f8f25

 Comment 9: There definitely is an issue with 8.2.2 on bower, but I can't duplicate the undefined issue. It seems there is a digest issue going on in that version.

I did verify that these versions work below

AngularJS Versions
- 1.3.0-beta.18
- 1.3.0-build.3001+sha.d2f8f25
- 1.2.2

Redactor 
- 9.2.5
- 9.2.6 

Can someone who's getting this issue give me a complete code sample so I can replicate.  I may not spend a lot of time on this sense radactor is paid and they are on version 9.2.6, but I'll do what I can .

 Comment 10: I had the same problem and I solved it by loading jQuery before angular and redactor.

 Comment 11: Sorry I've been MIA from this. I managed to get this working on mine, but it was so long ago I'm not sure what I changed. I'm at work at the moment so I don't have much time. Here is my updated directive, likely hacked and smashed together.

```
  angular.module('angular-redactor', [])
    .directive("redactor", ['$timeout', function ($timeout) {

return {
      require: "ngModel",
      link: function($scope, elem, attrs, controller) {
          controller.$render = function() {
              elem = $(elem);

              var updateModel = function updateModel(value) {
                scope.$apply(function () {
                  ngModel.$setViewValue(value);
                });
              };

              var options = {
                changeCallback: function() {
                      $scope.$apply( controller.$setViewValue(elem.val()) );
                  }
              };

              var additionalOptions = $scope.redactorOptions;

              var editor;

              angular.extend(options, additionalOptions);

              // put in timeout to avoid $digest collision.  call render() to
              // set the initial value.
              $timeout(function () {
                editor = elem.redactor(options);
              });

          };
      }
  };

}]);
```

 Comment 12: It seems to work fine with the latest version of redactor and a current
version of this directive, as long as you include everything. ;)
On Sep 2, 2014 8:27 AM, "Adam Greer" thomasjordan@example.com wrote:

> Sorry I've been MIA from this. I managed to get this working on mine, but
> it was so long ago I'm not sure what I changed. I'm at work at the moment
> so I don't have much time. Here is my updated directive, likely hacked and
> smashed together.
> 
>   angular.module('angular-redactor', [])
>     .directive("redactor", ['$timeout', function ($timeout) {
> 
> return {
>       require: "ngModel",
>       link: function($scope, elem, attrs, controller) {
>           controller.$render = function() {
>               elem = $(elem);
> 
> ```
>           var updateModel = function updateModel(value) {
>             scope.$apply(function () {
>               ngModel.$setViewValue(value);
>             });
>           };
> 
>           var options = {
>             changeCallback: function() {
>                   $scope.$apply( controller.$setViewValue(elem.val()) );
>               }
>           };
> 
>           var additionalOptions = $scope.redactorOptions;
> 
>           var editor;
> 
>           angular.extend(options, additionalOptions);
> 
>           // put in timeout to avoid $digest collision.  call render() to
>           // set the initial value.
>           $timeout(function () {
>             editor = elem.redactor(options);
>           });
> 
>       };
>   }
> ```
> 
>   };
> 
> }]);
> 
> —
> Reply to this email directly or view it on GitHub
> https://github.com/TylerGarlick/angular-redactor/issues/11#issuecomment-54168817
> .

 Comment 13: Well Im facing this same issue at the moment and Im using bower to download the lib as well! Its actually intermittent! Sometimes, the editor loads fine, other times it gives me this error. Help?

Oh and my jQuery is being loaded before any other lib, so I dont think that should cause a problem.

 Comment 14: I don't believe the bower version is current, you'll probably need to try
again with the purchased version and its most recent update.

On Tue, Oct 28, 2014 at 6:52 AM, Shashanka Nataraj <thomasjordan@example.com

> wrote:
> 
> Well Im facing this same issue at the moment and Im using bower to
> download the lib as well! Its actually intermittent! Sometimes, the editor
> loads fine, other times it gives me this error. Help?
> 
> —
> Reply to this email directly or view it on GitHub
> https://github.com/TylerGarlick/angular-redactor/issues/11#issuecomment-60757816
> .

 Comment 15: @Rosseyn Is right. I bought the cheapest version and it works fine with this library.

 Comment 16: I am seeing this as well. As a temporary fix I used `$($_element)` in place of `$_element`.

 Comment 17: I figured my issue out. Unrelated to this issue. It seems to be working properly now for me. 

 Comment 18: getting same:

`
TypeError: undefined is not a function
    at angular-redactor.js:55
    at angular.js:16223
    at completeOutstandingRequest (angular.js:4905)
    at angular.js:5285angular.js:11607 (anonymous function)angular.js:8557 $getangular.js:16226 (anonymous function)angular.js:4905 completeOutstandingRequestangular.js:5285 (anonymous function)
`
{'source': 'GithubIssues', 'repo_name_with_owner': 'TylerGarlick/angular-redactor', 'issue_id': 35729872, 'repo_stars': 209.0}