Lockdown the rewrite regex.

Ensure that only validly-formatted info hashes are handled. Improper urls are left with nginx's own 404 response.
Lockdown the PHP-FPM handler.

Prevent any possible PHP execution by explicitly defining the only PHP file that can be run (rather than a regex matching "any path ending in .php").
Correct typo
Merge remote-tracking branch 'origin/better_nginx_regex' into running

Conflicts:
	README.md