Fixed some review issues
Fixed some review issues

Fixed some issues that came up during review.
- Update section titles to have a full phrase
- Fix ${URL}
- Have short install script clean up after itself so it can be re-run.
- Small wording changes.

google/gvisor,google/gvisor,google/gvisor-website,google/gvisor,google/gvisor,google/gvisor,google/gvisor-website,google/gvisor,google/gvisor,google/gvisor