Added docs for UserGroups.
Merge branch 'master' of https://github.com/appacitive/appacitive-docs

* 'master' of https://github.com/appacitive/appacitive-docs:
  android push docs
  Fixed a faulty code snippet.
  Updated APUser, APDevice and APGraphNode documentation.
  refactoring android docs
  updated initWithAPIKey to registerAPIKey
  path parameter added while storing cookie
  fixed formatting
  switching to language using hash tag fixed
  fixed formatting
  fixed issue where if user lands with language selected in url it used to take him/her to previous selected language
  fixed the issue of font on large screen
  spell mistakes corrected. extra spacing from android section removed.
  removed hash in index.html
  added redirection in main index page