update readme

update readme
Merge branch 'dev'
Merge branch 'dev' of https://github.com/DragonBones/SkeletonAnimationLibrary.git
refine readme
Merge remote-tracking branch 'origin/dev'
Merge remote-tracking branch 'origin/dev'
Merge remote-tracking branch 'origin/dev'
Merge remote-tracking branch 'origin/dev'
update json
update
update
update
Added reverse play capability
update
Added masking support
Fixed masking registration issues
fix a typo
fix bug, flash player 10 flash.geom.Point don't have copyFrom method
fix bone multiple display pivot bug.
fix 360+ rotate bug.
change durationScale to duration
remove textureAtlas width and height