Added license info
Merge branch 'master' of github.com:willthames/ansible-inventory-grapher

Conflicts:
	bin/ansible-inventory-grapher
Don't link all groups to all group

Although all children are technically a child of all, it simplifies
the graph if we only link groups without other parents to all.
Fixed documentation and graphs to reflect recent changes
Allow groups to be graphed and output to go to stdout
Memoisation of parent group graphing
Improved documentation and options handling for stdout