Put simulation cleanup code in a try:finally block.
Merge branch 'master' into cleanup-on-fail

Conflicts:
	nengo_spinnaker/simulator.py
Allow simulation with no Nodes.

 - flake8
Don't appstop if loading hasn't taken place.
Merge branch 'cleanup-on-fail' of github.com:ctn-waterloo/nengo_spinnaker into cleanup-on-fail

Conflicts:
	nengo_spinnaker/simulator.py
Merge pull request #82 from ctn-waterloo/cleanup-on-fail

Put simulation cleanup code in a try:finally block.