SHTOOLS: Version 3.4

This release adds missing functionality to the SHGrids, SHCoeffs, and SHWindow classes, and adds support for PyPI.

• Add pyshtools to PyPI repository. Can now be installed using pip install pyshtools.
• Add new function SHBiasKMask which is the arbitrary window counterpart to the spherical cap window SHBiasK.
• Add get_biasedpowerspectrum() method to SHWindows for arbitrary windows.
• Add copy() method to all classes, which returns a deep copy of the instance.
• Add __sub__, __add__, __rsub__, __radd__, __mul__, __div__, __truediv__, and __pow__ operators for two sets of coefficient or grid classes, or one coefficient or grid class and a scalar.
• Add nwinrot option when rotating spherical cap windows in SHWindow that will rotate only the first nwinrot windows.
• Add degrees option to get_lats() and get_lons() methods.
• Add the constructor from_file() to initialize an SHGrid with a numpy formatted data file. Add option to read coeffs and grids from a numpy formatted binary file. Addtofile() methods to output raw grid and coefficient data as either text or binary formatted files.
• Update Intro 1 notebook and add example to Intro notebook 2 showing how to use arbitrary localization windows.
• Convert notebooks to html and add links to web documentation.
• Add option fixed_power to SHCoeffs.from_random() method to generate random coefficients that fit exactly the expected power spectrum.
• Add Earth topography coefficients referenced to mean sea level to the example files, expanded to degree 300: srtmp300.msl.