Greenworks v0.6.0 for NW.js v0.16.1 & Electron v1.3.3

• Greenworks complied for NW.js v0.16.1 with Steamworks SDK 1.37
• Greenworks complied for Electron v1.3.3 with Steamworks SDK 1.37
• API documents are moved from wiki to docs
• Add new friends APIs (Thanks for @marwanhilmi):
  • persona-state-change event
  • greenworks.getFriendsAccount(friend_flag)
  • greenworks.getFriends(friend_flag)
  • greeenworks.requestUserInformation(raw_steam_id, require_name_only)
• greenworks.getSteamId() now returns an object of SteamID