Issue title: .search-field input adding box-shadow
 Issue body: Is there a way to turn off the box-shadow I am seeing on .search-field input? It is taking on a bootstrap style but I cannot seem to override it with css therefore I am assuming the plugin is adding a focus after selection?

 Comments: 
 Comment 0: @infatti Can you reproduce in a [Fiddle](http://jsfiddle.net) and include a screenshot of what you're seeing?  What OS and browser?

(In the Fiddle, you can load up Bootstrap as an External Resource in the left sidebar.)

 Comment 1: You could try some of the CSS posted in #1336 

 Comment 2: @pfiller, @tjschuck is there any need to keep such 'question-issues' open? If the issue creator want to take action he or she can reopen the issue with a Fiddle as asked.

 Comment 3: Fine with me.  Closing this until the original poster comes back with more.

 Comment 4: I'm definitely in favor of closing issues that aren't well documented or include feature requests that will obviously not get added to Chosen. If people provide documentation of a problem, they can re-open or make a new issue.

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