apache_request_headers may return false on failure
travis: test against hhvm
Merge pull request #57 from FriendsOfSymfony/pr/apache-request-headers-failure

Handle apache_request_headers() non-array return values
Merge pull request #58 from FriendsOfSymfony/pr/travis-hhvm

test against hhvm
Fixed issue #59
Merge pull request #60 from steffenbrem/master

Fixed issue #59