Specify a version for Ember Data in the docs

[benkonrath]

Our docs currently specify the requirements as follows:

• Django REST Framwork >= 3.0
• Ember CLI >= 0.1.0

We also require Ember Data >= 1.0.0-beta.12 but I don't know what this implies for the version of Ember and Ember CLI. There's some information on the Ember blog about Ember 1.7 support being dropped in 1.0.0-beta.13 and it seems to recommend Ember 1.8.

http://emberjs.com/blog/2014/11/24/ember-data-1-0-beta-12-released.html

At the very least we need to add ED 1.0.0-beta.12 to the list of requirements.

[dustinfarris]

Ember CLI currently generates a requirement for ember-data 1.0.0-beta.12. I'm thinking we should peg the next release of ember-cli as the minimum supported version for two reasons:

1. I'm hoping the ember-cli-dependency-checker issue is resolved in the next release.
2. All new projects generated with ember new will be sure to meet our minimum ED requirement.

Notwithstanding all of that, noting the required ED version in the docs is a good idea.