Separate integration tests from unit tests #67
Description
We currently only have unit tests that run fast, mock out most of their dependencies, etc. We will also need integration (or end-to-end/system/functional/whatever) tests that test the complete system. An integration test might, for example, use pip2 to install a real project from GitHub and verify that the files were installed in the correct location.
Integration tests take considerably longer to run than unit tests. We should separate unit tests from integration tests so they can be easily run independently. What is the standard way of doing this? Should they be in different directories? Nose lets you add attributes to tests; should we use those to tag the integration tests? Etc...