Fix various issues

- Make sure that we are always referring to the local libraries and not
  the published Hackage packages!
    - This needs a `cabal-version` bump
- Make sure every component imports the default stanzas
- Add a `defaults` stanza for `default-language`
- Add a `tests-default` stanza for making sure test suites are built
  threaded
- Remove unnecessary warning-related `ghc-options`
- Use the `pedantic` stanza instead of manual checks for `pedantic`

Author: michaelpj