Bump plugin version to 3.4.0

Clears the deferred maintainer-review backlog (PRs #148-#150). Minor
version: emission now removes broker-side attributes that the current
issue representation no longer carries, which changes what an existing
broker entity looks like after an update. No migrations, no manual step.

Author: dkastl

init.rb

@@ -8,7 +8,7 @@
   author_url 'https://github.com/dkastl'
   url 'https://github.com/gtt-project/redmine_gtt_fiware'
   description 'Adds FIWARE integration capabilities for GTT projects'
-  version '3.3.0'
+  version '3.4.0'
 
   # Specify the minimum required Redmine version
   requires_redmine :version_or_higher => '6.0.0'