Allow ralouphie/getallheaders ^3.0.0
Allow ralouphie/getallheaders ^3.0.0

Allow "ralouphie/getallheaders": "^2.0.5 || ^3.0.0 in composer.json which drops PHP < 5.6 support

Also does some repo cleanup adding .gitattributes. Enables travis testing on PHP 7.0 and above

https://github.com/ralouphie/getallheaders/compare/2.0.5...3.0.0
guzzle/psr7