Add options for [--image] command.

[Uonlyliveonce]

If you want to use this tool in large project, you will get a much too crowded image. I have added ranksep & nodesep options for graphviz.

[dnkoutso]

Still want to merge this?

[Uonlyliveonce]

@dnkoutso Yep, i have changed yet. When i use default parameter, i get a messy image like this.

But when i use --image --ranksep=5 --nodesep=.5, the result like this

I know that our project must be more graceful. But i dont'n want to get a useless image when i use this plugin.

[segiddins]

Thanks!