[riak] Configured RiakKVClientTest.java to work with default bucket-type instead of creating a new one.

[travis] Added riak-admin commands to create and activate test bucket.

[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.

Fixes #438

[travis] Fixes #389 - Update .travis.yml to use the container based infrastructure for Travis Builds.