Apply yapf to meep.adjoint.*

[ianwilliamson]

This PR applies YAPF to meep.adjoint.* via the command:

yapf -p -i *.py

which uses the default PEP8 style.

[stevengj]

@smartalecH, I'm okay with merging this, are you?. If you have a large PR pending we can wait to merge that first, but in any case the procedure outlined in #662 should work to automate rebasing any branches you are currently working on.

[smartalecH]

@stevengj sure, I'm fine with rebasing my upcoming PR when it's ready. Thanks for asking.

[stevengj]

Instructions for rebasing other branches after this PR:

Replace MYBRANCH below with the name of your branch:

# update repo
git checkout master && git pull origin master # update master

# switch to your branch
git checkout MYBRANCH

# rebase onto PREVIOUS commit
git rebase 2d90872abe0ea96ca22ebaf1cf029c3948f4547d

# reformat and rebase to THIS PR's commit
yapf -p -i python/adjoint/*.py
git commit -a -m "reformat"
git rebase -Xtheirs 483b0557eca81db35013cb9f5c688f497b711b5a

# finish rebase
git rebase master