Maybe pr_pause() should pull after switching back to master

[jennybc]

Inspired by this:

> pr_pause()
✔ Checking that local branch 'no-rd' has the changes in 'origin/no-rd'
✔ Switching back to 'master' branch
> pr_init("dontrun-avoidance")
✔ Checking that local branch 'master' has the changes in 'upstream/master'
Error: Local branch 'master' is behind 'upstream/master'.
Please use `pr_pull_upstream()` to update.

Happens if a PR is merged and you don't know that and you use pr_pause() as opposed to pr_finish().

[hadley]

Agreed