Sns-toolbox

In this update, we have added support for an enhanced spiking neuron and synapse model. This is backwards compatible with previous versions, so existing code should not be affected.

Additionally, we fixed an issue with SNS_Iterative where spiking synapses were not being updated correctly. Going forward this backend will not be updated, and as such we do not recommend it for new designs.

What's Changed
* Fixed bug with incorrect reseting by wnourse05 in https://github.com/wnourse05/SNS-Toolbox/pull/46
* Updated spiking model by wnourse05 in https://github.com/wnourse05/SNS-Toolbox/pull/47


**Full Changelog**: https://github.com/wnourse05/SNS-Toolbox/compare/v1.4.2...v1.5.0

Fixed rendering such that matrix connections are now supported, rendered same as pattern connections.

**Full Changelog**: https://github.com/wnourse05/SNS-Toolbox/compare/v1.4.1...v1.4.2

Added support for defining connection matrices between populations. Added support for 1x1 kernels to pattern connections.

**Full Changelog**: https://github.com/wnourse05/SNS-Toolbox/compare/v1.3.1...v1.4.1

Adjusted synapse creation such that conductance values of 0 are supported.

Ran benchmarking experiments.

**Full Changelog**: https://github.com/wnourse05/SNS-Toolbox/compare/v1.3.0...v1.3.1

What's Changed

* Redid rendering, renderer is now separate from networks so graphviz is not mandatory to use core sns_toolbox functionality
* Neuron objects now support resting potentials other than 0 mV
* Networks now operate in V space instead of U space
* Synapses now are defined using Elo and Ehi instead of R
* Networks can be run with no inputs
* Documentation added about rendering networks
* Documentation added about saving and loading networks
* Updated equations in documentation to match software implementation
* Documentation added about building networks
* Added documentation on simulating using a GPU
* Added installation and citation instructions


**Full Changelog**: https://github.com/wnourse05/SNS-Toolbox/compare/v1.2.0...v1.3.0

- Neurons with voltage-gated ion channels are now available for use within all backends
- Networks can be reset, either to their initial state or a new, user-defined state.