Make HtmlAttributes class public

Need to expose this class and add render method overloads that accept it
in order to allow other libs to pass merged html attribute values in
Added tests for new render methods
Set up Razor view extensions

Added BoostrapHelpers to provide access to bootstrap renderer methods to
Razor views, and a base view class to initialize the BootstrapHelpers
Merge pull request #3 from bernos/setup-razor-project

Setup razor project