Add unit test of collapse module !
Add test
Reformat placeholder module and add placeholder unit test!
Update some files
pull upstream
merge
Add Carousel module!
Reformate some modules!

Changed collapse to click a button will close the siblings node
Add unit test for Carousel module!
Modify some codes of collapse!(Not important)
Resolve conflict!
Merge pull request #14 from alfredzh/dev

accept pull request from alfredzh/dev