Release v0.1.1

• implemented custom port painter for different port shapes. #160
• implemented NodeGraph.node_selection_changed signal #167
• fixed issue #176
• fixed issue #173
• refactor clean up on NodeTextItem logic for editing text and text now has selection highlighting.
• to enable edit mode on node name is now remapped on double-click instead of single-click.
• add more doc strings.
• updated docs.

Example for customising port shapes.
https://jchanvfx.github.io/NodeGraphQt/api/html/examples/ex_port.html#creating-custom-shapes