README: drop defunct gemnasium badge

README.md

@@ -1,6 +1,6 @@
 # JSON Test Data Generator
 [![Gem Version](https://badge.fury.io/rb/json_test_data.svg)](https://badge.fury.io/rb/json_test_data)  [![Build Status](https://travis-ci.org/danascheider/json_test_data.svg?branch=master)](https://travis-ci.org/danascheider/json_test_data)  [![Code Climate](https://codeclimate.com/github/danascheider/json_test_data/badges/gpa.svg)](https://codeclimate.com/github/danascheider/json_test_data)
-[![Coverage Status](https://coveralls.io/repos/github/danascheider/json_test_data/badge.svg?branch=master)](https://coveralls.io/github/danascheider/json_test_data?branch=master)  [![Dependency Status](https://gemnasium.com/badges/github.com/danascheider/json_test_data.svg)](https://gemnasium.com/github.com/danascheider/json_test_data)
+[![Coverage Status](https://coveralls.io/repos/github/danascheider/json_test_data/badge.svg?branch=master)](https://coveralls.io/github/danascheider/json_test_data?branch=master)
 
 The JSON test data generator takes JSON schema as input and generates test data matching the specification. You can download it from RubyGems:
 ```ruby