README unclear about running specs [JIRA: CLIENTS-42]

c.f. @boosty

> I just checked out the current master of this repo and it seems the only things you need to run the tests are: 
> 1) a running riak instance
> 2) a copy of spec/support/test_client.yml.example as spec/support/test_client.yml
>
> I guess if this would be made clear in the README, this ticket could be closed. Or am I missing something?
>
> Btw.: I came to this issue because today I started preparing our extensions mentioned by @skaes. My goal is to submit the pull requests in the next days.