Compress (gzip) files when they're uploaded.

[mbhall88]

Use zlib within node.js to compress files when they are uploaded. This will reduce storage space required in the future.

[mbhall88]

Look into a way of checking if the file being uploaded is already compressed. NB: there are many compressed formats so look into whether this can be handled efficiently without have to do a million if statements to check the file extension.