Support local-only projects
Render src filepath correctly without quotes
Merge branch 'master' into feature-local-only
Allow specifying the location of the source code
Update usage
Support all VCS that have a nix-prefetch script

We now use the various nix-prefetch-* scripts to fetch the source. This
makes it easy to add new sources, and also makes the code simpler.

A side effect is that we now generate a `fetchurl` source for hackage
packages, using the `hackage` mirror.

This depends on NixOS/nixpkgs#3038 and NixOS/nixpkgs#3039
Don't generate fetchurl for hackage packages
Merge branch 'master' into feature-local-only

Conflicts:
	src/Cabal2Nix/Hackage.hs
	src/cabal2nix.hs
Add zip fetcher
add Distribution.NixOS.Fetch to doctest libs
add missing extension pragma (needed for doctest)
update release.nix
Merge remote-tracking branch 'origin/master' into feature-local-only

Conflicts:
	src/Distribution/NixOS/Derivation/Cabal.hs
	src/hackage4nix.hs
Merge pull request #59 from bennofs/feature-local-only

Support local-only projects