adds post model
adds application serializer

need to set the primaryKey used by ember-data to reflect the key used by
mongo
adds http-mock for ember-data tests
adds mocks for posts
adds application adapter for api namespace
setups testem to run tests against http-mocks

need to setup a proxy in testem, so it will run against the http-mocks
when testing

the downside to this approach is that we'll now need to run `ember
serve` before running our test suite
adds index route for posts