Antimony 0.7.5

This is a pretty minor release feature-wise, but it's got a few simple fixes that will speed up performance when designing large models.

Features:

• More nodes (thanks, Neil!).
• Limit size of script output window.
• Adding str input type for scripting

Bugfixes:

• Cache certain types of lookups to make redrawing graph window faster.
• Improve node change detection to make adding new nodes faster.