Completely support all standard list.sort args in Structure.sort and
IStructure.get_sorted_structure.
Improve doc.
Update change log.
Switch to yaml for input sets. Proper use of YAML Cloader where available.
Make sure setup.py includes yaml files.
Fix json loading.
Update YAML install instructions to include libyaml.
Merge remote-tracking branch 'mpmaster/master'

Conflicts:
	setup.py