Ensure github repos being processed are unique

In one case, four gems all referenced the same repo, and I created
4 issues. See

https://github.com/mrhenry/lalala-ng/issues/38

lalala-test 4.0.0.dev.198
lalala-development 4.0.0.dev.198
lalala-assets 4.0.0.dev.198
lalala 4.0.0.dev.198