Add option to unminify minified files

[oBusk]

Some packages only publishes minified code, would be nice to be able to still make a diff of them.

This opens for lot's of issues obviously. This would mean we can't rely on libnpmdiff in the same way we do currently, since we would want to diff the two unminified files. We could look closer at the code of libnpmdiff and then try to replicate it to get a serviceable functionality.

Probably a bit heavy to do automatically for all files? But it would be cached I suppose. Other option is to have some button in the UI to do it on demand in browser and then do a diff between the resulting files.