Integration tests fail for Pull Requests in Travis

[jantman]

See e.g. https://travis-ci.org/jantman/awslimitchecker/jobs/72610593#L711

When Travis checks out a pull request, it checks out the merge of the PR to master, i.e. git fetch origin +refs/pull/45/merge. The git-based integration tests (Test_AGPLVersionChecker_Acceptance.test_install_git_e_dirty, Test_AGPLVersionChecker_Acceptance.test_install_git_e and Test_AGPLVersionChecker_Acceptance.test_install_git) attempt to install awslimitchecker from GitHub using the commit hash of the current git checkout that the tests exist in - which, in this case, is the merge hash, which doesn't exist yet in the repo.

Options that I can think of:
(1) don't just check out whatever hash the test repo is at, if it doesn't exist in origin.
(2) Look at the value of the TRAVIS_PULL_REQUEST environment variable, and do something different in the integration tests if we're testing a PR (such as installing +refs/pull/$TRAVIS_PULL_REQUEST/merge instead of the SHA).

[jantman]

This has been released in 0.1.1, which is now live on pypi.