Add clang-format

[matthew-reynolds]

Pull Request

Closes #60

Duplicates changes from uwreact/frc_control#34 and uwreact/frc_control#35. This entails adding a clang-format config file, CI rules, and updating the README and PR template.

Contribution Checklist

• [x] I have read the contributing guide.
• [x] I have referenced relevant issues.
• [x] I have labeled accordingly.
• [x] I have detailed my changes as much as possible.

Change Checklist

• [x] I have added tests.
• [x] I have added necessary documentation.
• [ ] I have tested my changes on real hardware.

[matthew-reynolds]

Looks like the build is failing because our ROS version is still set to Kinetic in our CI config, which uses Ubuntu 16, which doesn't have clang-format-7 available. This CI config issue is addressed in #58, which is ready for merging. In future, I shouldn't have made that change in that PR, it should have been separate. However, since #58 is about to land anyways, let's just leave this PR until then rather than going back and breaking it out.

[wmmc88]

Waiting on review from @michaelwm ?

[wmmc88]

@Matthew-Reynolds update and merge?