Multiple small fixes

1. Added support for text format (or "raw body response" wrapped in xml) 39d3ff4
2. Added the github issues link in the meta.xml file 4a16900
3. Added some doc in the readme (supported format and API) 0053a56
4. Made static calls to `prepareGateway` consistent 5819b41

Should this become version 2.1 ? I will gladly add a commit that does so if necessary.