[travis] Added Riak service for testing purposes. [riak] Added test unit. [riak] Set eventual consistency as default in both README.md and riak.properties file, as strong consistency it's not the main model adopted by the db (check http://docs.basho.com/riak/kv/2.1.4/developing/app-guide/strong-consistency/ for further info). [riak] Fixed getFields() function by transforming it into createResultHashMap(). This function creates the HashMap to give as result appropriately. [riak] Removed scan transaction support for strong consistency model. 2i search is not allowed for this model, neither there is a suitable search mean to use to achieve a proper scan transaction. [riak] Done minor fixes to code and comments.