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
Merge pull request #1970 from Daxter/bugfix/1927-travis-ci

[1927] Get Travis CI working
Removed body.active_admin encapsulation for global-reset.
Removed body.active_admin encapsulation for other active admin styles..
Merge branch 'unencapsulate-css-global-reset' of https://github.com/tinynumbers/active_admin into unencapsulate-css-global-reset