Implement ministerSelect jQuery plugin

It's build on jquery.autocomplete and it allows ministers to be selected using auto complete field. The plugin operates with the original <select> element, which is also submitted to the server
Made ministerSelect to accept a class and use form-control to format it

This is to support Firefox mainly
Improve the ministerSelect to comply to jQuery naming convention
Use the autocomplete lookup instead of traversing DOM elements
Update govuk_frontend_toolkit
Use colours for ministerSelect from the govuk_frontend_toolkit gem
Move bootstrap and kendo assets to vendor folder
Use select2 stylesheets from the gem and only override required changes
Improve stylesheet require
Merge pull request #70 from ministryofjustice/improve_minister_select_widget

Improve minister select widget