[Pulp-list] updated pull request conventions

[Austin Macdonald]

Hello pulp-list,

I have recently updated our docs to reflect a slightly modified set of
conventions for pull requests.

https://pulp-dev-guide.readthedocs.org/en/latest/contributing/index.html

The changes are summarized here:

1. Development branches should be stored on the developer's GitHub fork.
Pull requests will take place from there, preventing pollution of Pulp's
branch list.

2. Bugfix branch names no longer need a user name since they are on the
developer's fork. Branches should be named by their BZ number and an
optional message, ex. `123456 - fixes that bug`. Also the primary commit
message of this branch should follow the same convention of `<bz id> -
commit message`.

3. Feature branches should similarly not include user names. Feature
branches should start with `feature/` to differentiate them from bug
branches, ex. `feature/cool-thing`.

Thanks,
Austin Macdonald