Add Annul operation
Added missing annul_response
Gitignore .DS_Store
Cleaned up tests

Testing now requires a valid netaxept test token.
Removed build status

Travis is no longer responsible for CI builds,
this is because we need a token and a merchant ID to test.
Bumped the version
Set homepage in gemspec
Renamed 'amount' parameter to 'transactionAmount' in AUTH, SALE, CAPTURE and CREDIT
operations. Partial capture did not work because of this.