Add interface for helpcenter
Change client so as to support "helpcenter" option
Add "article" api for helpcenter
add client interface for help center
Add categories api
add translation api
add api for translation
add api for articleComments
add api for subscriptions
add api for article labels
add api for votes
add api for search
add api for search
add api for access policies
add api for article attachments (create not implemented)
merge windows version
update Readme for helpcenter api
Merge branch 'docs', add readme for api help center
simplify client.js, less confussion
Merge pull request #45 from nnabuuu/master

Add support for helpcenter