Adding documentation/comments to the .htaccess file.

Apologies for sending this to the wrong branch before--I'm new here, and didn't realize that was standard, and somehow missed the line in the README. Thanks for pointing it out.

I think I'm sending it to the right place now, but if I've still got it wrong, let me know.

This commit is just expanding the comments in the .htaccess file. I'd like to make some similar changes to comments in other files, so let me know if I'm on the right track here.