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
Right now it asks me to choose from:

      conflict Unable to find suitable version for ember-i18n
        1) ember-i18n 2.2.2
        2) ember-i18n ~2.9.0
    [?] Answer: 1

It ignored my selected option and wrote `~2.9.0` to my bower file.

I reproduced it after:

    rm -rf bower_components/ember-i18n/
    bower cache clean
    ember generate ember-i18n