Add and remove all the files in one git command

[asmeurer]

This might fix #324.

[asmeurer]

This ran pretty quick for me adding 10000 empty files.

[asmeurer]

And I can confirm my test is slower the old way, even though they're empty files, by about a minute and a half. https://travis-ci.org/drdoctr/doctr/jobs/430365436.

@thequackdaddy can you try running your build against this branch (install doctr from this branch)?

[asmeurer]

Or I can try it out myself tomorrow if you don't get to it.

[thequackdaddy]

Nice. You shaved 25 minutes off the build!

https://travis-ci.org/thequackdaddy/statsmodels/jobs/430370425

[asmeurer]

Awesome. We should still figure out how to only add the changed files to shorten the output size in the log, but I'll leave that for a future PR.

[thequackdaddy]

Thanks for the fast turnaround on this.

Do you plan to release to pypi soon? Otherwise, I will make a PR on statsmodels to install from master here.