rewrite clone and extend funciton
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/base/_core.js
Merge remote-tracking branch 'origin/master'
Merge remote-tracking branch 'origin/master'
Merge remote-tracking branch 'origin/master'
Merge remote-tracking branch 'origin/master'
Merge remote-tracking branch 'origin/master'
rewrite clone and extend funciton