Remove `Ember::VERSION`

It should be defined in `ember-source`.
Merge pull request #182 from tricknotes/remove-ember-version

Remove `Ember::VERSION`
Register sprockets engine in config.before_initialize.
This fixes template compilation on Rails 4.0.0.rc1.
added ember data warning message to readme
Merge pull request #187 from kagemusha/ember-data-warning

added ember data warning message to readme
Update README.md
remove RC version requirements.

please specify the correct version of ember-source and handlebar-source
in your gemfile.

eg.

```ruby
gem 'ember-rails'
gem 'ember-source', '1.0.0rc3.3'
gem 'handlebars-source', '1.0.0rc4'
```
update readme
correct readme indentation
fix ember-source and handlebars-sources versions
fix failing tests, and remove gem files, no longer 
reference in the Appraisals file
add ruby 2.0.0 tests (and make them work)
Remove description about latest version

The version described in README.md is too hard to keep maintenance.
Merge pull request #194 from tricknotes/remove-version

Remove description about latest version
update readme, for latest version dependencies.

Once we are out of rc's we can stop with this madness.
fix version references
rails generate ember:install --head now just fetches from the cdn
generated router should provide a simple and update to date example
coffee and js store's should be generated the same
add useful doc links to generated files