Upgrade to the latest submodule version (compatible with moment.js 2.8)
Update to the latest submodule version
Update to the latest version of the submodule
Bumped version to 3.1.1
Merge branch 'eonasdan version 3.1.1'

Main changes included in this version:
- submodule upgraded to version 3.1.1 of Eonasdan bootstrap-datetimepicker
- compatible with momentjs version 2.8.1
- momntjs dependency is included in the Gem's Gemfile