I've been using http://yUML.me for this sort of thing:
For example code like this:
// Cool Class Diagram [Customer|-forname:string;surname:string|doShiz()]<>-orders*>[Order] [Order]++-0..*>[LineItem] [Order]-[note:Aggregate root]
will yield a flow chart like this:
It's fully text based, and you can even use the text to make a link like:
http://yuml.me/diagram/plain/class/edit/%2F%2F Cool Class Diagram, [Customer|-forname:string;surname:string|doShiz()]<>-orders*>[Order], [Order]++-0..*>[LineItem], [Order]-[note:Aggregate root]
Disclaimer: I am in no way affiliated with yUML.me