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'
Merge remote-tracking branch 'origin/dev'
Merge remote-tracking branch 'origin/dev'
Add modify to bone data, and support spine bone inherit rotation and scale control supports.
Modify object data.
Add blend mode support
Merge pull request #33 from watsonsong/master

Add bone and slot support and blend mode support.
Merge remote-tracking branch 'remotes/origin/master' into dev
Fix some typos.