Now using Sass for CSS, adding mocha as test suite and some basic tests

  * now using Sass, css related to the BlockView is now compiled
  * now using mocha to test the behaviours of BlockView:
    * implemented basic test on the behaviours of the different event
      emitters dom element of the BlockView
    * some custom mouse events are prepared for some further heavy
      behaviour testing
  * gruntfile was updated to take account of Sass and grunt-mocha