Pytmd

fix: extrapolate for equirectangular case to address 87
feat: added global Empirical Ocean Tide model (82)
feat: added Arc2kmTM to list of available models
feat: option for changing time standard in file programs
feat: ICESat and Operation IceBridge updates
refactor: slim down requirements.txt

- refactor: using python logging for handling verbose output (71)
- fix: Operation IceBridge functions for geotrajectory outputs (73)
- feat: try to get grid mapping attributes from netCDF4 and HDF5 (74)
- refactor: adjust longitude convention based on model longitude (76)
- feat: add TPXO9-atlas-v5 to standard models (77)
- feat: add tide program for ATL10 freeboard files (78)
- feat: added function to calculate a tidal time series (80)

* refactor: use model class for files and attributes
* feat: can use numpy datetime arrays as input time variable
* feat: calculator for height differences between ellipsoids
* feat: can use argparse prefix files to define command line arguments
* feat: added generic list from Apache http server
* fix: netCDF4 cases where there is no mask on constituent files
* fix: USAP now requires capchas
* fix: pole case in stereographic area scale calculation
* fix: use getncattr to get attributes from netCDF4 files to prevent deprecation errors
* ci: install proj from source for cartopy dependency
* test: NSIDC no longer requires authentication headers
* test: added test for model definition files

conda and docker releases
add new Gr1km-v2 1km Greenland model from ESR
add option for extrapolation cutoff in kilometers
add warning for tide models being entered as string to address
bug fixes for nearest-neighbors and bilinear interpolations
documentation updates

Preparations for conda-forge release

semantic versioning with setuptools_scm
documentation update with contribution guidelines
citations within documentation
generically named ICESat/ICESat-2 files
ocean load tide fixes
update manifest files

* Simplified inputs to netcdf, GOT and FES tide read programs to be similar to binary OTIS program
* Added `TPXO9-atlas-v4` in [single constituent OTIS file format](https://www.tpxo.net/global/tpxo9-atlas)
* Updated documentation for consistency and to add contribution guidelines
* Add checks to extrapolation program to prevent runtime exceptions
* Updated spatial module adding polar stereographic area scale calculation
* Updated spatial module adding routines for cartesian coordinate conversion
* Prevent `ComplexWarning` for fill values when calculating amplitudes 44
* Prevent numpy `DeprecationWarning` for `np.bool`, `np.int` and `np.float`