Integration tests

I think the project would benefit from integration tests. Bugs that PRs like #35, #89, and #97 would be easier to observe with integration tests.

Here is some initial simple code for the purpose of discussion. Things to consider:

* in general do we want this?
* I've put all the existing tests into "unit" — does that seem appropriate?
* currently there is no HTTP mocking framework and a real request is made to facebook. what mocking framework do we like? the two I have used are fakeweb and VCR. fakeweb is simpler and takes less DSL syntax to apply the mocking to the entire suite. in the absense of other factors, I would use fakeweb. VCR is more featureful and more actively developed. perhaps others have more experience with these or other projects and are more opinionated.

This should require `helper.rb` instead