v6.7.0

Sorry for the hiatus everyone. I moved to Denver (from South Africa x_x) and was busy with admin and large projects for an entire year. The good news is that I am now using this library in two large projects at work and so it will most likely get updates more quickly. Im also planning a version 7 which will break up the library further so that the rendering is completely pluggable. I plan on eventually doing a WebGL version so we can build impossibly large diagrams similar to those in the excellent Unreal and Blender pipelines.