Bugfix release

This fixes a major breaking bug (#150), which pertains to the TIGER api.

In the long run, I'm hopeful to be able to merge/integrate to @walkerke's pygris to supplant our tigris/mapservice code, since there is probably a better way to interface with these mapservices which none of @cenpy-devs are experienced in using.

Product API

This release adds the long-running product API, which adds a direct interface to the US Census Bureau using placenames.

In addition to a ton of work on the product API, a number of bugs, issues, and enhancements were added.

1. docstrings were improved and made more consistent throughout the library.
2. a website (cenpy-devs.github.io/cenpy) was built to house the documentation for the package, alongside use cases that show how users can access the product API and developers can build on top of the cenpy primitives to make their own products.
3. error handling for requests was improved in cases of choppy or filtered internet connections.
4. a bug in the geometry requests was fixed.
5. variable filter/searching was improved, in filter_variables (cenpy.products) or varslike (cenpy.remote)
6. tests were improved & continuous integration updated to take into account better defaults in conda-forge

CRSs and PySAL 2.0

This release works on a few distinct changes:

1. #33, #35 fixing and making more informative the errors that are raised by incorrect or malformed queries.
2. 151b85bf Moving to PySAL's 2.0 architecture.
3. d1422917 trying to use the coordinate reference system correctly for data gained from the API
4. A Zenodo release, providing a DOI for the package.