Compliance-checker

- Major refactor of CF Checks for Chapter 1 - 6
- Inclusion of many more example datasets into unit tests
- Tighter integration between CF checks and the feature detection introduced by NCEI's checked `cfutil.py`
- Fixed several feature mis-identification issues with regards to coordinate checks and reduced-horizontal-grids.
- Improved result titles and corrective action messages

Backports 331 and 334 onto 2.3.0 release to fix issues with `flag_masks` attribute.

New Features:
Run compliance checker on metadata files (`*.cdl`). Testing large NetCDF files
could take a long time. Now you can reduce that time by checking compliance
against a metadata text file representation of the data. Use the NetCDF Utility
ncdump to generate a `.CDL` file and use the compliance checker against the
metadata file to get your score.

CF standard names are checked against the standard name table version specified
in the global attribute `:standard_name_vocabulary`. If the version specified is
not the version packaged with compliance checker, that version will be
downloaded and used in the standard name check.

Are there checks that are taking too long to run? Now you can skip checks using
the command line. Use the `-s` flag and specify the name of the check function
you wish to skip. For example


compliance-checker -s check_high


Enhancements have also been made to the compliance checker web version
[https://data.ioos.us/compliance/index.html](https://data.ioos.us/compliance/index.html).

Now you can batch process files hosted on an OPeNDAP server using the new
compliance checker web API. Refer to the wiki for details:
[https://github.com/ioos/compliance-checker-web/wiki/API](https://github.com/ioos/compliance-checker-web/wiki/API)

Descriptions for each of the checkers and helpful resources are now available.

Bug Fixes:
- Save text output to file from the command line
- Remove unnecessary CF check - check_alternative_coordinates
- Updated the packaged CF Standard names table to v36
- Added NODC sea names check to gliderDAC.
- Fixes bug that was overwriting JSON output when multiple checks are performed

- Added type checking to results returned from checkers
- Added netCDF4 to explicit requirements
- Default to utf-8 output if encoding is not explicitly set
- Fixed issue where cf_role variables were being detected as geophysical variables
- Cleaned up the CLI's parsing of command line arguments
- Fixed python3 setup errors
- Added code version information to checker
- Removed alternate coordinates check
- Added support for dynamically downloading standard name table
- Added support for metadata only checks

- ACDD 1.3 now supported.
- A method of selecting checker version has been introduced.
- Check Suite Name, Version, and other metadata can be defined in the checker class and shown in output.
- Several outstanding checker bugs have been addressed.
- Several new checks have been added per Git Hub issues.

Ensure only stable versions of Compliance Checker from PyPI are installed