[conda-build-config] Update scikit-image version

See merge request !2

This commit fixes the following issues:

- Partially addresses #7 by proposing a way to check README file syntax
  through python packaging (twine)
- It introduces arguments to the subcommands `ci pypi` and `ci readme`
  that provide the package path instead of letting it figure out from
  the environment/variables (also addresses #8 in this case)