Point to Unzip/tar from Decompress docs and errors

[leouieda]

If given a .zip or .tar archive, Decompress will now tell users to
use Unzip and Untar instead. This clears up the confusion around why
Decompress doesn't work with zip files. Add a pointer to the
docstring as well.

Fixes #184

Reminders:

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst and the base __init__.py file for the package.
• Write detailed docstrings for all functions/classes/methods. It often helps to design better code if you write the docstrings first.
• If adding new functionality, add an example to the docstring, gallery, and/or tutorials.
• Add your full name, affiliation, and ORCID (optional) to the AUTHORS.md file (if you haven't already) in case you'd like to be listed as an author on the Zenodo archive of the next release.