fix issue #72
Fix last implicit self retain warning
Added completion block after presentation
update README
Updated completion blocks
updated README
updated README
fix issue #73
fix issue #74
fix issue #7
updated README
Added preferredContentSize support (see issue #26)
fix issue #26
fix issue #75
Update README and Demo
fix issue #76
fix issue #76
Merge branch 'master' of https://github.com/nicolaschengdev/WYPopoverController
fix issue #77 and issue #78
updated Demo