Support applying patches to dependencies

[andir]

Sometimes there are NPM packages that do not behave as expected. One common example is packages relying on paths of binaries or insisting on downloading their own binaries. Beside the linking abilities that we already have it might also be good to be able to patch packages.

On my initial work on this project I came across a bunch of binary packages, most notably this this PR could be added as a patch to gain more sane behavior of the package.

This would be follow-up work to nix-community#24