Fix spelling.
Add FoldingFailedException.
Fix some flake8 complaints.
Remove unneeded isinstance check.
Have RNAalifold extract locations from postscript.

This now will add a .locations property to the result from RNAalifold. This
represents the locations extracted from the postscript file this program
generates.
Include bounding box from RNAplot postscript.

This also includes information about the bouding box produced by RNAplot in the
results from running RNAalifold.
Version bump.