Release version 2.0.0

This plugin has been around for a while and in production in many Redmine
installations. The current 0.2.0 version didn't do this justice.

Bumping all the way to 2.x to signal the compatibility with Redmines 2.x line.
Going forward major version numbers should follow Redmines major versions.

init.rb

@@ -4,5 +4,5 @@
   name 'Redmine Github Hook plugin'
   author 'Jakob Skjerning'
   description 'This plugin allows your Redmine installation to receive Github post-receive notifications'
-  version '0.2.0'
+  version '2.0.0'
 end