Display the latest released gem version.

The reason I used an HTML img tag here is to support Retina 
resolution wherever possible.

This is something we're working on for all Shields metadata badges in general but Michael from Gemfury already supports it:
http://badge.fury.io/for/rb/bundler
Merge pull request #2785 from olivierlacan/patch-1

Display the latest released gem version.
Feature of Summarize all the using gem bundle-feature- 33 added
Merge branch 'master' of https://github.com/bundler/bundler