Update getRoomIdFromName- return null if not found

Remove dependency on robot adapter findFlows since it will always
return something - by default, the identifier passed to it - even
if a flow is not found

All callers appear to handle the possibility of this returning null

lib/flowdock-util.js

@@ -1,12 +1,14 @@
 // A collection of adapter-helpers for hubot on flowdock
 
 function getRoomIdFromName(robot, roomName) {
-  if (!robot.adapter.flows || !robot.adapter.findFlow) {
-    // in some cases, returning the room name will bork things, so we should log
-    robot.logger.info(`getRoomIdFromName couldn't find flow id for ${roomName}`)
-    return roomName
+  if (!robot.adapter.flows) {
+    return
+  }
+  for (let flow of robot.adapter.flows || []) {
+    if (roomName.toLowerCase() === flow.name.toLowerCase()) {
+      return flow.id
+    }
   }
-  return robot.adapter.findFlow(roomName)
 }
 
 function getRoomNameFromId(robot, roomId) {