Added description
New script to build frequency-response curve

Good for figuring out what output firing rate to expect given the input
parameters.
Building the frequency-response curve for HH neurons
Appears to be working correctly (untested).

No spikes fire with current configuration: Must up the weight.
Properly plots frequency-response curve

Produces a 2D color plot (imshow) which shows the firing rate for
combinations of excitation and inhibition. Assumes weights are fixed.
Simple paramater changes