Remove --proxy requirement / tests

- Remove --proxy requirement
- Remove pretender and use jquery-mockjax instead ([reason](https://github.com/dockyard/ember-cli-proxy-fixtures/pull/18#issuecomment-58458387) [source](https://github.com/trek/pretender/commit/5c49c5e9b77f0ff7f7d3dc0132f25d608fc2ceaf) )
- Add a generator to add jquery-mockjax
- Add test-suite

refs #16