Minor additions
Adding done tactic
working on porting HSet
remove an extra definition of HProp from Empty
Merge branch 'master' of git://github.com/HoTT/HoTT

Conflicts:
	theories/HLevel.v
	theories/HProp.v
	theories/HSet.v
Merge branch 'master' of git://github.com/HoTT/HoTT
added a few lemmas.  "cancel" now means "unwhisker".
fix a couple things in the 'done' tactic
Merge branch 'cancel'