Improve Bond Visualisation

This release introduces additional configuration/functionality for visualising bonds:

• bond_radii_scale: Factor to scale atomic radii by, when computing bonds (via overlapping radii)
• bond_array_name: The name of a boolean array on the ase.Atoms, specifying which atoms that bonds should be drawn for
• bond_pairs_filter: A list of bond element pairs to filter by
• bond_color_by: How to color bond: 'atoms' (same as connecting atoms) or 'length'
• bond_colormap: The matplotlib colormap to use with ``bond_color_by='length'`
• bond_colormap_range: The matplotlib colormap normalisation to use with bond_color_by='length'

Also, document testing was moved to CircleCI and numpy pinning was bumped to 1.19

Improve documentation

Merge pull request #11 from chrisjsewell/develop

Release v0.3.1

First pypi release

Merge pull request #3 from chrisjsewell/develop

Release v0.3.0