Added UpdateUtility. Fixed JSONModel (now  handles above 100 followed channels)

UpdateUtility: now able to check for new updates on a server.
ConfigWindow: can now tell user if there's a new version, also a new
"prompt" property
View: Added ability to retrieve icons (might need to revise this)

Added Vert.x library to the core of the application (used for handling
asynchronous requests to update server)

JSONModel: Now able to retrieve more than 100 followed channels, but API
requests are unoptimized.

Rest of changes are related to update manager...
Merge branch 'master' of https://github.com/xx-k/twitchnotifier_src