S3-site-cache-optimizer

- Add support for gzipping text-based files, and setting the right headers for such files.
- Bugfix for failing rewrite operations when an asset occurred more than once on the same line.

- Added support for webm and mp4 assets.
- Added region parameter, that allows you to connect directly to the endpoint of a specific AWS region.
- Added prefix parameter, that allows you to write to a subdirectory of a bucket.
- Added domains parameter, that includes a list of domains to consider your own when searching for assets in HTML/CSS.

First feature-full release with a lot of fixes for rewriting assets, and a lot of cleaning up.

First release of the CLI with all intended features, but with limited support for the rewritables' contents.