added a few neuron model examples
added Morris-Lecar example
added Hodgkin-Huxley example
small updates to hh plotting
added integrate-and-fire example with refractory period
Added integrate-and-fire model with synapse
removed unnecessary variable s from iaf example
some tweaks to synaptic example
added theta neuron model
added proper input to theta model
added Pinsky-Rinzel CA3 neuron model
added FitzHugh-Nagumo model
updates to FHN model
added hindmarsh-rose mode
using consts in adex model
added Wang, Rinzel, Rogawski model
Merge branch 'master' of https://github.com/iraikov/Sims.jl
updated hh and izh example for reentrant branch
initial refactoring for reentrant support
refeactoring examples for use with reentrant branch