Add /lmgtfy and /lmbtfy commands

`/lmgtfy SignalR Documentation` becomes:
![lmstfyscreenshot](https://cloud.githubusercontent.com/assets/1687386/3526921/2f4c5274-0780-11e4-9298-44a41efc5f28.png)
This was clearly a bug (mine).
I have changed both to `SendMessage`. I've also removed the `user` parameter from this method as its not used anywhere (add confusion as this `user` parameter isn't used to send the message as assumed).
This is building (and generalising) on what *was* the `GenerateMeme` method ([introduced here](https://github.com/JabbR/JabbR/commit/a8e4db6feeabe1cda7e859a66fa49004cd51f129#diff-929c50cc9143b4a6b528e721c2c1a1b6R32)).