Xdoctest

Changed

* The xdoctest "analysis" option now defaults to "auto" everywhere.

Fixed

* Fix issue 112 `--analysis=dynamic` argument is now respected

Changed

* Added GitHub actions to the CI
* Disabled workaround 16806 in Python 3.8+
* New CI GPG Keys: Erotemic-CI: 70858F4D01314BF21427676F3D568E6559A34380 for
reference the old signing key was 98007794ED130347559354B1109AC852D297D757.


Fixed

* Fixed minor test failures
* Fixed 106 - an issue to do with compiling multiline statements in single mode.
* Fixed 108 - an issue to do with compiling semicolon token in eval mode.

Changed
* Removed the distracting and very long internal traceback that occurred in
pytest when a module errors while it is being imported before the doctest is
run.
* Pytest now defaults to `--xdoctest-verbose=2` by default (note this does
nothing unless `-s` is also given so pytest does not suppress output)

Fixed
* Bug in REQUIRES state did not respect `python_implementation` arguments
* Ported sphinx fixes from ubelt

Changed
* Directive syntax errors are now handled as doctest runtime errors and return
better debugging information.

* README and docs were improved

Changed
* Better message when a pytest skip or exit-test-exception occurs

Fixed
* Suppressed warning about using internal `FixtureRequest`