Add Bitdeli Badge

Author: amacneil

README.md

@@ -388,3 +388,5 @@ For more information, see the [example application directory](https://github.com
 **Please provide feedback!** We want to make this library useful in as many projects as possible.
 Please raise a Github issue, and point out what you do and don't like, or fork the project and make
 suggestions. **No issue is too small.**
+
+[![Bitdeli Badge](https://d2weczhvl823v0.cloudfront.net/adrianmacneil/omnipay/trend.png)](https://bitdeli.com/free "Bitdeli Badge")