Pyemap

Bug fixes:

- Fixed bug associated with sequence alignment when non protein residues are not placed at the end of the chain. Had no effect on the back end, but cause visualization bugs and occasional crashes on the web server.

- Remove CairoSVG dependency
- Make pygraphviz optional
- Remove deprecated Biopython call to MUSCLE, make compatible with new MUSCLE API

In version 2.0, PyeMap is now capable of mining protein graphs for shared ET pathways/motifs. This is available under the
pyemap.graph_mining modules.

Changelog:

**Single Protein**

- Automatic identification of redox-active metal ions
- Support for pathway visualization in nglview widget
- New degree-based edge pruning algorithm
- User control over residue depth and RSA thresholds for determining buried/surface exposed

**Graph Mining**
- gSpan and pattern matching algorithms
- Control over substitutions and edge thresholds
- Sequence and structural based clustering of protein subgraphs
- Support for subgraph visualization in nglview widget

**General Improvements**
- Improved SMILES strings for standard amino acids and ET active moieties
- Improved visualization of residues using RDKit
- Remove wget dependency, use [requests](https://pypi.org/project/requests/) to fetch files

Hot fix for compatibility issues. We now pin to Pillow 7.2.0, and remove some tests which were causing issues with newer RDKit.

Bug fixes:
- Fixed type checking for original atom ID
- Fixed NGL visualization for residues with insertion codes