v0.2.0

This version completely overhauls the Python API and command-line tools. The major
changes are:

• Support for projecting properties onto surface faces and isoline segments. The
  command-line utilities include support for group velocities and spin texture.
• New tools for calculating Fermi surface dimensionality and orientation based on
  the connectivity across periodic boundary conditions.
• New tools for calculating Fermi surface properties such as area and for averaging
  projections across the Fermi surface. This enables the calculation of Fermi velocities.
• New visualisation tools for Fermi surfaces and slices with projections. Fermi surfaces
  can now be colored by the surface properties. Additionally, vector properties
  can be indicated with arrows. This allows for the visualisation of spin texture.

Command line changes:

IFermi now has a new command line interface. There are two subcommands:

• ifermi info: for calculating Fermi surface properties and dimensionalities.
• ifermi plot: for visualisation of Fermi surfaces and slices.

API additions:

• FermiSurface and FermiSlice objects now support projections.

• Added Isosurface and Isoline classes.

• Added many analysis functions to the FermiSurface and FermiSlice modules.

• New analysis module containing algorithms for:

  • Calculating Fermi surface dimensionality and orientation.
  • Uniformly sampling isosurfaces and isolines.
  • Determining the connectivity of isosurfaces and isolines.
  • Interpolating and smoothing isolines.

API changes:

• fermi_surface module renamed surface.
• FermiSlice class and related functions moved to slice module.
• plotter module renamed plot.
• interpolation module renamed interpolate, and Interpolator class
  renamed FourierInterpolator.