Updated GelfHandler/GelfFormatter

Changes monolog to use the updated official graylog2/gelf-php
Allow for both mlehner/gelf-php and graylog2/gelf-php usage
Merge remote-tracking branch 'official/master' into gelf-php-compat

Conflicts:
	composer.json
Merge remote-tracking branch 'bzikarsky/gelf-php-compat'
CS fixes, refs #326