Fix ::Gentoo QA warnings

[Kangie]

Closes: #35

@thesamesam looks fine to me, I decided to call this 0.6.0 and do some other housekeeping. There doesn't seem to be any unit tests but the output against real ebuild targets looks good.

If you'd sanity check, tag, and update ::gentoo I'd appreciate it!

Edit: target/debug/cargo-ebuild ebuild --manifest-path ./Cargo.toml looks really good

[joakim-tjernlund]

@gyakovlev ping?

[dongsupark]

Any chance this PR could be merged?
I just hit the issue of cargo-ebuild not being able to deal with the new CRATES syntax. i.e. @ instead of -.

[thesamesam]

I don't have commit access to cargo-ebuild although I could give it to myself given gyak is AWOL. FWIW, we recommend using pycargoebuild now if yo ucan.

[dongsupark]

@thesamesam Thank you for the info.
pycargoebuild seem to work well in my Gentoo VM. However, that tool relies on Gentoo specific paths.
Ideally I would like to generate ebuild files on both Gentoo and non-Gentoo systems. cargo-ebuild is perfect for the purpose. But it is too bad not being actively maintained.