Issue title: Call to undefined function Webklex\IMAP\Query\camel_case()
 Issue body: Please be aware that these issues will be closed if inactive for more then 14 days :)
![image](https://user-images.githubusercontent.com/15870174/64246481-712a5600-cf3f-11e9-90b7-e7cbd8d604df.png)
![image](https://user-images.githubusercontent.com/15870174/64246491-7687a080-cf3f-11e9-8cc8-99a2510a3cb0.png)
![image](https://user-images.githubusercontent.com/15870174/64246514-7f787200-cf3f-11e9-949d-443b0dbf1bec.png)

 Comments: 
 Comment 0: Hi @k3youmin ,
which laravel version are you using? `camel_case` is a laravel helper function:
```php
if (! function_exists('camel_case')) {
    /**
     * Convert a value to camel case.
     *
     * @param  string  $value
     * @return string
     */
    function camel_case($value)  {
        return Str38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5mel($value);
    }
}
```
 Comment 1: [image: image.png]

On Wed, Sep 4, 2019 at 9:34 PM Webklex <heather88@example.org> wrote:

> Hi @k3youmin <https://github.com/k3youmin> ,
> which laravel version are you using? camel_case is a laravel helper
> function:
>
> if (! function_exists('camel_case')) {    /**     * Convert a value to camel case.     *     * @param  string  $value     * @return string     */    function camel_case($value)  {        return Str38d1:d2b4:3d06:83e8:96a5:8c2:893d:aba5mel($value);    }}
>
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{'source': 'GithubIssues', 'repo_name_with_owner': 'Webklex/laravel-imap', 'issue_id': 489068346, 'repo_stars': 517.0}