[arvados-dev] handling github pull requests

[Peter Amstutz]

We've had our first pull request! 

https://github.com/curoverse/arvados/commit/e60990e8ccc42495fb8ec1afe53bb47b1b604866

Ward and I had a discussion on how to handle working with contributers
through github.  Here's what we've decide:

1. We've created a branch on github called "staging" that will be
updated in parallel with "master"
2. Github pull requests should be merged into the "staging" branch by a
developer with curoverse/arvados github commit access.
3. A developer with commit access to the arvados.org repository can pull
the changes from the "staging" branch.
4. That developer merges the changes into "master," and pushes the
changes to arvados.org.
5. The changes will be reflected in arvados.org "master", which will be
automatically mirrored from arvados.org to github.

One of the goals is to be good github citizens, so that outside
contributers get credit for their pull requests.

- Peter