Hacked about to make it work. Some of these changes are genuine bug fixes, others are hacky changes. Too tired to sort them out right now, but it should be done.
Fun and games
Hacky-hacks for a hacky branch.
Fix mouth, prevent nodes having negative charge. Change some parameters.
Tidied up most hacks.

Conflicts:
	creature/creature.go
	entitymanager/consts.go
De-hackied more code
Fixed all UTs.
Worth a shot.
Want to fix travis before merging...
Removed reliance on random numbers for interpreter_test
Doh\!
Fix to mouths to prevent creatures occasionally getting stuck on each other.