Added feedforward layout.

Not perfect, but works pretty well on even reasonably complex networks.
Look at neural_extraction.py in the gui to see the algorithm failing,
but even there you can still make sense of it.
Made code for the new layout algorithms play nice.

Leaving non-feedforward as default for now. Set the feedforward
variable in server.py to True to enable the feedforward layout.
Merge branch 'master' of https://github.com/ctn-waterloo/nengo_gui

Conflicts:
	static/js/main.js
Fixed conflicts in last commit
corrected subnet containment checking
safer import of partial gui specification
making layout more robust to large networks
layout works with manual typing
remove zoom mode option from display
removed drag resize due to flakiness
Merge branch 'master' of https://github.com/ctn-waterloo/nengo_gui
Updated readme
Update README.md
corrected config syntax

deleted fewer nodes on reload
fixes #73
fixes #74
small fix to init logic
added feed fwd button and behaviour
fixes #79
fixed filemenu hiding