Refactored `PubSub` and `Frontier` initialisation and multiton factories
Using `JSON.stringify` to display object in error message to avoid `[Object object]` string which doesn't give any information
Added topic constants to `HttpRequestAciton`

 - `LATEST_HTTP_REQUEST_SUCCEEDED`: executed when `HttpRequestAction` operation succeeded.
 - `LATEST_HTTP_REQUEST_FAILED`: executed when `HttpRequestAction` operation failed.
 - `LATEST_HTTP_REQUEST_DONE`: executed when `HttpRequestAction` operation is done (either failed or succeeded).
Implemented dispatching of following topics automatically from `HttpRequestAction`

 - `LATEST_HTTP_REQUEST_SUCCEEDED`: executed when `HttpRequestAction` operation succeeded.
 - `LATEST_HTTP_REQUEST_FAILED`: executed when `HttpRequestAction` operation failed.
 - `LATEST_HTTP_REQUEST_DONE`: executed when `HttpRequestAction` operation is done (either failed or succeeded).
Unit and integration tests
Updated version in `bower.json` to 0.2.8
Merge branch 'develop'