get Travis CI working

## Changes

### Misc
- reordered Gemfile -- shouldn't change functionality
- fix test env builder to support Rails versions properly

### Issues
- #1966
  - fix missing `decorator_method` for Draper
- #1967
  - remove 1.9 hash syntax
  - fix I18n dynamic re-translation feature

### Travis
- use latest Rails maintainence releases
- use latest Bundler version
- remove REE & 1.9.2
- add 2.0.0