Add Gentoo to documentation + cleanup

I've noted the fact that trlinkin/nsswitch now supports the Gentoo Linux
distribution, as well as clean up some other issues in the `README.md`
file.

With any luck, I've removed most of my more embarrassing typos, spelling
errors, and bad grammar. Now I only have poor grammar.

Stretch Goal: Sound less stupid more of the time.
Bump version for 0.0.8 release