Next previous, updates to getArticle

- Implemented new POST method to the API client
- Implemented nextPreviousArticles() in API ArticleResponseMaker
- New ArticleNavigationTransformer class to forma the response of the
next/previous article data
- Slight re-work of Article controller to update params to sub channel
from channel. Now calls POST method of API client
- New IOC bindings for ArticleNavigationTransformer
- new getNextPreviousArticles() ArticleRepository function
Merge branch 'next-previous-articles' into dev-150714-1115

- ArticleResponseMaker now returns next and previous article indicators
- New ArticleNavigationTransformer to convert results of new previous
and next article items
- New IOC bindings for ArticleNavigationTransformer
- New getNextAndPreviousArticles method for ArticleRepository