fixed typo

lib/index.js

@@ -216,7 +216,7 @@ var determine_type = function(variations){
 	    } else{
 		var modified = get_modifier(variations[k]);
 		if(unit_database[types[i]][modified.unit] !== undefined){
-		    posible.push({'type': types[i], 'unit': modified.unit, 'modifier': modified.modifier});
+		    possible.push({'type': types[i], 'unit': modified.unit, 'modifier': modified.modifier});
 		}
 	    }
 	}