Simple ember-cli support.

It is very simple ember-cli support that uses addon mechanism. 

When used in ember-cli project it:
* provide a generator to install cldr and ember-i18n as bower components
* imports cldr and ember-cli to application build
* setup configuration

To use it in ember-cli project:
```
npm install ember-i18n --save-dev
ember generate ember-i18n
```

Implements issue: https://github.com/jamesarosen/ember-i18n/issues/129
updated to `i18n-plurals`