Pensa

- Rewrite H-bond feature functions to use MDAnalysis (angle + distance criterion)
- Retain the old functions (only a distance criterion) for quick screening

- Major clean-up of the library structure
- Functions not imported by main module anymore, need to import respective submodule.
- Adapted tutorial to new functions
- Hydrogen bonds as features
- Removed dependence on mdtraj, replaced PyEMMA features with MDAnalysis and its other functionality with deeptime.

- uncertainty estimate via blocking
- option to add chain ID to distances

General CSV read/write function for features.

- feature subset selection
- reader for CSV files with DrorMD features
- Bar plots for eigenvalues and PCA correlations

Major additions:

- Metrics that summarize the similarity of two ensembles in one number: `pensa.comparison.metrics`
- A general sorting function: `pensa.preprocessing.coordinates.sort_coordinates()`