dropbox: Add basic jIO connecter

Work like Qiniu one so far
dropbox storage: add allDocs and jslinted
dropbox-storage: add basic remove
dropbox-storage: implement removeAttachment
dropbox-storage: Do some JSlint
dropbox: pass first test (Post & Get)
dropbox: pass Put & Get tests
dropbox: indent and pass PutAttachment and getAttachment
dropbox: pass remove tests
dropbox: allDocs tested
dropbox: clear storage before allDocs Tests
dropbox: beautify tests
dropbox: jslint connector
dropbox: finish js lint on tests