Ability to add memes while running, also grumpy cat

Added the ability to tell hubot to add a new meme from memegenerator while hubot is running.

The new command is `hubot add meme /new meme regex (.*),(.*)/i, 1, 2` with two regex groups for the two lines and where `1` is the generatorID and `2` is the imageID.

I also added grumpy cat.