chirp: 20180512 -> 20180519

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/chirp-daily/versions.

These checks were done:

- built on NixOS
- Warning: no invocation of /nix/store/s2g23ds5fsnl0bg7dyn9j5y3drvxs3ar-chirp-daily-20180519/bin/.chirpw-wrapped had a zero exit code or showed the expected version
- Warning: no invocation of /nix/store/s2g23ds5fsnl0bg7dyn9j5y3drvxs3ar-chirp-daily-20180519/bin/chirpw had a zero exit code or showed the expected version
- 0 of 2 passed binary check by having a zero exit code.
- 0 of 2 passed binary check by having the new version present in output.
- found 20180519 with grep in /nix/store/s2g23ds5fsnl0bg7dyn9j5y3drvxs3ar-chirp-daily-20180519
- directory tree listing: https://gist.github.com/a05ef55580a6032a5b40aabb92e6dfd7
- du listing: https://gist.github.com/13517a738616514609c44b95f30fc5a1