Effmass

This release gives more flexibility for locating extrema of interest in the bandstructure. It allows you to generate segments
i) in the valence band only
ii) in the conduction band only
iii) in the "frontier bands" only (highest energy valence band or lowest energy conduction band)
iv) for a particular direction

This might be useful for high-throughput type studies where manual inspection of the generated segments is not desirable.

A minor release with no breaking changes.

Includes additional unit tests and updates to the tutorial docs.

There are three changes in this release:
- Support for the open-source [Octopus](https://octopus-code.org/wiki/Main_Page) (TD)DFT code
- Support for vasprun.xml files (previously a procar file was required for Vasp compatability)
- A fix for compatability with the latest version of FHI-aims

The main change is that there is now a CLI option for saving a summary file (of user inputs and calculated effective mass values). This is important so that there is a record of the calculation done (to enable reproducibility).

The other change is that dependencies are handled more efficiently. The packages needed for testing or docs are only available when specified (using `pip install effmass[tests]` and `pip install effmass[docs]`) and are not required for standard install.

This is a bug fix for an error that was thrown when using the Castep CLI without specifying the Fermi level.

This is a major release which enables:
- effmass to read in Castep output files
- effmass Data object to be instantiated with an ASE bandstructure object

**As a result of these changes, the `Data` class has been renamed `DataVasp`.**

This release also includes a command line interface for calculating parabolic effective masses.

- Support for FHI-aims calculations