Pyjams

* round_microseconds method for `datetime` class if dates are from
non-microsecond precise origin.
* Added return_arrays keyword in `date2num`.
* calendar keyword takes precedence on calendar attribute of
datetime objects in `date2num`.
* Add left, bottom, top to standard layout options in `mcPlot`.
* Documented as_cmap keyword of `get_cmap`.
* Added `means` to calculate daily, monthly, yearly, etc. means.
* Allow scalar input in `num2date`.
* Renamed `datetime.py` to `class_datetime.py`.

* Allow negative dates in `date2date`.
* Support of microseconds in `date2date`.
* Assure that `input2array` gives no 0d-array.
* More `datetime` tests and bug fixes for microseconds and has_year_zero.
* Delete unnecessary HDF5 filters in variable definition in `netcdfio`
for compatibility with netcdf4 > 1.6.0.
* Reduce precision to 14 digits for tests of `logistic2_offset`.
* Remove Python version 3.7 from CI but leave version 3.6 because of
problems with netcdf4 for 3.7 on Windows.

* Removed documentation from `Read the Docs` and moved to Github Pages:
https://mcuntz.github.io/pyjams/
* More `datetime` tests and bug fixes.

* Added module `datetime` with class `datetime` that mimics cftime.datetime
but for non-CF-conform calendars. It also adds the functions `date2num`
and `num2date` for conversion between datetime objects or string
representations and numerical times. It adds the convenience wrappers
`date2dec` and `dec2date` for easier portability of older code using
JAMS.
* Allows more usage of helper functions `input2array` and `array2input`
by allowing undef=None in and making it the default.
* Make netCDF4 an requirement of ``pyjams``.
* Use I/O type helpers in `str2tex`.
* Use I/O type helpers in `date2date`.
* Allow strings and string arrays in `array2input` and `input2array`.
* Add kwargs mechanism to `plot_save` in `mcPlot` to pass arguments
to save_file.
* Add --transparent as a standard option in `mcPlot`.

* Added module `ncio` with netCDF4 functions to copy netcdf files while
doing some transformations on variables and dimensions.
* Added shape keyword to `infonetcdf`.
* Assert that at least one of nc, snc, cname, or sname is given in call to
`xread`.
* Change from NCL amwg to pyjams amwg as the default color palette in
`mcPlot`.

* Added `pyjams_amwg` color map.
* Bandwidth h output of `kernel_regression_h` is scalar if one-dimensional.
* undef=np.nan is default in helper functions `array2input` and
`input2array`.
* Array masked or set to undef only if shapes of array and input agree in
`array2input`.
* Output of `kernel_regression` now has the type of `y` and not `x` or
`xout`.
* `get_color` can get list of colors and not only single colors.
* Register ufz colors only once with `get_color`.
* Add `print_colors` to print known named colors to console.