added a link in README.md which points to a blog post on using versionist. 

The blog post  [API Versioning using Versionist](http://www.multunus.com/blog/2014/04/api-versioning-using-versionist/) could serve as an additional resource for developers for integrating versionist in their API. It basically explains the need for versioning and the STEPS involved in versioning current API and also STEPS involved in subsequent versioning.

PS:This blog post was featured in the first edition of [RubyIndia](http://www.rubyindia.org/issues/1)