Add a 'Like Pokemon' feature

[cartogram]

This is a common example in the relay docs, but I've not seen it implemented with a actual graphQL service. Something like https://facebook.github.io/relay/docs/guides-mutations.html#a-complete-example, with the viewerDoesLike field on the Pokemon Type. This is a very common requirement and would be great to see an end to end example using Graph.cool

[marktani]

I think this is a nice addition to #39. Do you think that this would thematically fit best to the mutations chapter?

An addition like that should always be reflected in the pokedex app as well, which means that for the moment I prioritize more separated issues first, but thanks for the suggestion anyway! 👍