Update Resources on "Dotted Version Vectors"

Removed the link to  "Evaluating Dotted Version Vectors in Riak", since "Improving Logical Clocks in Riak with Dotted Version Vectors: A Case Study" is the extended version of the first.
Also added a direct link to the official paper on Dotted Version Vectors "Scalable and Accurate Causality Tracking for Eventually Consistent Stores".