Option to prefer gz files.

[DylanPiercey]

Coming from https://github.com/cloudhead/node-static, they have a "gzip" option that when enabled will automatically serve any .gz files in a directory and fallback to un gzipped variants.

Would it be possible to add a similar option here? I understand that a compression middleware would be most effective in many cases but it would be a handy option to have.

[dougwilson]

Are you referring to the progress going on in pull request #108 ?

[DylanPiercey]

@dougwilson looks spot on. Thanks for pointing this out.