add more exception handling while scraping dotfiles
add more exception handling while scraping dotfiles

Summary: Also adds the ApiRateLimitExceededError exception to `get_api_page`.

Test Plan:
We skipped over the problematic
https://api.github.com/repos/rveens/dotfiles/contents/vimundobackup/.vimundobackup?ref=master
due to GitHub's improper escaping of URLs in their implementation of HATEOAS.
Also, I exceeded github's rate limit and this correctly reported that and exited
gracefully.

Reviewers: spicyj, xymostech

Reviewed By: spicyj

Differential Revision: http://phabricator.benalpert.com/D129

vim-awesome/vim-awesome,jonafato/vim-awesome,vim-awesome/vim-awesome,vim-awesome/vim-awesome,shaialon/vim-awesome,starcraftman/vim-awesome,vim-awesome/vim-awesome,starcraftman/vim-awesome,divad12/vim-awesome,jonafato/vim-awesome,divad12/vim-awesome,starcraftman/vim-awesome,divad12/vim-awesome,jonafato/vim-awesome,divad12/vim-awesome,vim-awesome/vim-awesome,shaialon/vim-awesome,jonafato/vim-awesome,shaialon/vim-awesome,shaialon/vim-awesome,starcraftman/vim-awesome