Close #318: Add model/collection for loops.
Close #320: Added view for loop function.
Revert "Close #320: Added view for loop function."

This reverts commit ba87e91342f886b1c74e3cc25fdd1285e7006c02.
Revert "Close #318: Add model/collection for loops."

This reverts commit f084e269e27604a83de70ddbbdc5c13e47d16648.
Fix #322: The last loop is no more interrupted at the end of the video.
Fix #323: The loop selection is now done through a slider.
Close #325: Tooltips added to "next/previous loop" buttons.
Close #324: The loops are now created from the current playhead.
Close #326: Add visual representation for the loops.
Close #319: Complete unit tests. Add use of sinon.js for mocks and spy and blanket to test the code coverage. The loop view has been updated as well with input to enter loop length.
Fixed #333
Fixed #339: It was only a parameter "editable" to pass to the timeline item.
Fixed #334
Fixed #335
Fixed #336
Fixed #337
Close #338
Fixed #341
Fixed #342
Fixed #343