Added message interface 
Added message interface 

Added message interface to account for known and unknown keys
borisyankov/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped,mcliment/DefinitelyTyped,magny/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,magny/DefinitelyTyped,dsebastien/DefinitelyTyped,borisyankov/DefinitelyTyped,georgemarshall/DefinitelyTyped,markogresak/DefinitelyTyped