add virtual keyboard view
Merge commit 'f09aabfe91b9e22d1c06f234615c14245b0d0e39' into develop
merge slkhq
Merge branch 'master' into develop

Conflicts:
	Examples/Messenger/Messenger/MessageViewController.m
add virtual keyboard
add virtual keyboard toolbar demo gif
修正virtual keyboard部分 横屏的部分问题, 但是旋转仍旧异常
fix iOS8 retrate virtual keyboard