fix build failure

(https://travis-ci.org/gitlabhq/gitlabhq/builds/3593153)
Update `binding_of_caller` version

Updating this dependency fixed my Ruby 2.0 installation issues.
Restyle flash message. Not it does not overflow head panel
remove unnecessary center tag in devise layout
Merge branch 'master' of git://github.com/gitlabhq/gitlabhq
Enumerize gem added
Issue tracker field added to projects
Issue tracker added to edit project form in admin area
Project issue tracker functions refactored
External issue tracker params added to config
New field added
Migration added
Issues helper improved
Issues helper included to markdown helper
Wrong default section in config. Fixed.
Default value for issues_tracker setting added
Section name returned back to base
Gem gon added. It produces server-side variable values in javascript
Default issue tracker name added to gon variables
Issues tracker settings enableds/disableds without page reloading now