Added Bower support, moved Grunt to devDependencies

* Added Bower configuration (bower.json)
* Moved Grunt to the devDependencies in package.json
* Modified README to inform about the Bower support
Minor improvements and added option to pass array of HTML el to constructor
Added PUT and DELETE request support to AJAX

* Added request types support: PUT and DELETE
* Added Content-Type: application/json header when dataType = json
* When dataType = json, Browserkit tries to parse the response to json. If an error occures it falls back to text