Merge pull request #8 from aboudreault/mcq-tip-popup

Display tips & general feedback for MCQs like for MRQs, in a side popup.
minor fix for extra spaces
oups, indent-level-js was set to 2
Merge pull request #9 from aboudreault/answer-min-characters

Answer min characters
Ensure LightChild block are compatible with XBlock: added has_children to class Tip
Merge pull request #13 from aboudreault/html-in-tip

Ensure LightChild block are compatible with XBlock
max_attempts should be global to the mentoring block