Merge branch 'hotfix/2.4.3' into develop

* hotfix/2.4.3:
  fixed sprockets with updated version
  fixed Gemfile.lock
  gems upgrade, including Rails 4.1.0
switched from plain Bootstrap3 template to AdminLTE and added Gravatar support
updated CHANGELOG
Merge branch 'release/2.4.4'

* release/2.4.4:
  updated CHANGELOG
  switched from plain Bootstrap3 template to AdminLTE and added Gravatar support