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
Update README.md

No need for a `-o -` argument to be passed to the inventory grapher to output to stdout
First attempt at adding variables to graph
Mostly fixed variable graphing

Graphs now contain more accurate variables (overridden variables
are removed from parents, inherited variables are removed from
children)

Made it more testable by modularizing the graphing functions
Added tests to validate that variable inheritance is displayed
correctly.
Made writing to stdout default

The usage instructions already said this but now
reality reflects this.
Improved display of nodes and variables

Fixes #11
Updated documentation to use newly generated graph

Now that graphs now have variables, that should display
in the README
Hopefully fixed image URL in markdown this time
Allow suppression of variable display in graphs

You can turn off variable display with `-q` or `--no-variables`.

This turns into a template variable called `showvars`, and
templates can interpret that as expected (the default template
does this).

Fixes #12.