Updated root readme
Merge branch 'feature-documentation' of github.com:rc1/COSMObjectiveC into feature-documentation

* 'feature-documentation' of github.com:rc1/COSMObjectiveC:
  COSMSubscribableDelegate
  COSMSubscribable
  COSMRequestable
  COSMModelDelegate
  COSMModel
  COSMModel
  COSMModel
  COSMFeedCollection
  COSMFeedModel
  COSMDatastreamModel
  COSMDatastreamCollection
  COSMDatapointModel
  COSMDataPointCollection & COSMDataPointCollectionDelegate
  COSMAPI