remove warning for RAILS_ENV == test; use dev variant for test env.

fixes #184
Merge pull request #202 from fivetanley/default-to-dev-variant-in-test-environment

remove warning for RAILS_ENV == test; use dev variant for test env.
Remove unnecessary `bundle exec` in README.md

`bundle exec` is not required to run rails commands.
Merge pull request #203 from nragaz/patch-1

Remove unnecessary `bundle exec` in README.md
Add appraisal for rail4.0.0.rc1 and ember rc5
Namespace accessing Rails.env

Fixes bug introduced in 8600986e635c1b102b66700e0b211ed7a4400d38
Merge pull request #204 from kurtisnelson/master

Fix bug introduced in 8600986e635c1b102b66700e0b211ed7a4400d38
Remove unnecessary `Ember::Handlebars::VERSION`

It couldn't specify from ember-rails because it depends on handlebars-source.
Merge pull request #205 from tricknotes/remove-handlebars-version

Remove unnecessary `Ember::Handlebars::VERSION`
bump gem version
Update README.md
Better documentation for engine choice
Updated revision number for DS.Store

Update revision number from 11 to 13
Bump instructions to use latest ember rc6
Merge pull request #216 from machty/patch-1

Readme refers to new 'ember-source', '1.0.0.rc6.2'
added mixin directory
Update README to mark optional step as required

This step appears to be required, as I couldn't get it to work without executing it.  Lazy programmers will skip this -- thinking it's optional -- and then experience problems.
Merge pull request #222 from clekstro/patch-1

Update README to mark optional step as required
add bootstrap generator options in README
Merge pull request #223 from ccarruitero/readme

add bootstrap generator options in README