Filfinder

`threshold_adaptive` in skimage was slightly altered, causing issues for FilFinder.

Other notable changes:
- `radial_profile` was updated to be more robust for removing variations due to overlap with different objects (`auto_cut`)
- Tools for finding the width along the main filament branch (profiles across each skeleton pixel) were introduced in `fil_finder.width_profiles`.

The radial profiling did not work with the newest numpy release. This patches that problem.

Biggest updates are to the documentation and tutorial.

The keyword `save_png` has been added to save png plots and allow interactive plotting to be avoided for large maps.

The output tables have been fixed for individual skeleton branches. HDF5 tables are now supported and are encouraged for the branches (since the different number of branches in each skeleton makes it difficult to include in a single table).

There were some small mistakes treating the non-parametric width method properly, as well as the beamwidth conversion to physical units.

This release marks the version actually used in the accompanying paper.

FilFinder algorithm functionality is complete. This version is used for the results in the accompanying paper.

Functionality in the Analysis class is not yet complete.