First attempt at post-pruning dendrograms.
Moved post-pruning into Dendrograms.
First attempt at merging branches.
Clean-up removal section.
Use isinstanceto check is_independent.
Merge failed leaves into siblings.
Revamped pruning scheme. Iterates until all pruning is done.
Use fill_footprint. Removed re-assigning idx.
Set recursive to False.
Copy _stuctures_dict for keep_structures.
Added pruning test.
Add .all() to test.
Tweak post prune logic, min_delta criteria
Merge pull request #1 from ChrisBeaumont/master

Tweak post prune logic, min_delta criteria
Style change to post_pruning.
Changed post_pruning to prune.
Docstrings for new helper functions.
Extend comparison test to index maps.
Update name to prune in tests.
Removed min_value, added warnings and updates for params, minor docstring changes.