Support for multi white listed urls with regex url match.

Sample Command to run multi whitelisted urls with regex.

./google_auth_proxy \
  --redirect-url="http://yourcallbackurl.com/oauth2/callback"  \
  --google-apps-domain="yourdomain.com" \
  --upstream=http://127.0.0.1:8080 \
  --cookie-secret="nuts"\
  --client-id="your client id" \
  --client-secret="your client secret"  \
  --cookie-expire=0h30m0s \
  --cookie-https-only=false \
  --white-listed-urls="/hello.php","/status.php","/health-check-url/*"
Let's make this always perform a regex match so it's easier to reason about what's matched, and move the regex compilation outside of the request loop so we can give error feedback if invalid regex's are compiled sooner (ie: at startup).