Merge pull request #1 from satiani/master

Add instructions to run the yellowdemo instance
Merge pull request #2 from satiani/master

Implement example of verifying signatures of Yellow\'s IPN requests
Merge pull request #3 from satiani/master

Fix HTTP Status Code
Merge pull request #4 from satiani/master

Comment about nonces
verify the SSL
migrate to v1 api format
fix URL again
whitelist yellowpay.co
whitelist yellow_server for testing purposes