Support Tikz format in LaTeX renderer

[jackburridge]

In the LaTeX output it would be nice to have the option to support Tikz. This is possible in plantuml and would give better typographic consistency.

[jackburridge]

I've had an initial stab at the thing and it works quite nicely I just can't figure out if theres a cleaner way to do it, lots is missing as well(width, height, scale), the branch is available here:
https://github.com/jackburridge/plantuml/tree/tikz

I do a direct write to body to use \input{} and also add tikz to the preamble
demo.pdf
demo.zip

[yuja]

Thanks, the change looks fine to me. It's simple and small.

can't figure out if theres a cleaner way to do it,

Can you add a short # TODO: blah, blah... comment describing things should be cleaned up?

lots is missing as well(width, height, scale),

That should be fine since this is a new feature which breaks no existing use cases.
Unsupported options can be documented in README.