empty repos

[eshellman]

https://github.com/GITenberg/United-States-Declaration-of-Independence_1 is empty, but it shouldn't be.

check for other empty repos

[rdhyee]

@eshellman has asked me to check what other repos are empty like https://github.com/GITenberg/United-States-Declaration-of-Independence_1

[rdhyee]

In https://github.com/rdhyee/nypl50/blob/master/empty_gitenberg_repos.ipynb, I've developed a functioin repo_is_empty for computing whether a given github3.py repo is empty.