Add NEST examples

[HarshKhilawala]

Reproduced same example of NEST - One Neuron using PyNN.

References:

• NEST Example: One Neuron Example

• NEST Example: One Neuron Noise Example

• NEST Example: Two Neuron Example

• Model: Leaky integrate-and-fire model with alpha-shaped input currents

[HarshKhilawala]

@apdavison Requesting review and docstring changes

[HarshKhilawala]

@apdavison Also Added One Neuron Noise Example. Please review and share docstring convention for PyNN

[HarshKhilawala]

Added two neuron example in simple networks from NEST

[apdavison]

Thanks for these @HarshKhilawala. These are rather simple examples, but they are helpful since they match examples in the NEST documentation.

[HarshKhilawala]

@apdavison Here, my approach was to get familiarity with PyNN codebase so I considered implementing simple network from NEST with PyNN. But I do acknowledge my lack of prior experience in neuroscience.

Even with simple networks, I am facing some issues.

I have a separate PR for this where I request you to please review my code. (PR has changes linked to all files)

Refer to PR#802

[coveralls]

coverage: 63.264% (-0.07%) from 63.329% when pulling ce7a8681c29397f9d8379edf5775b3d273a4383c on HarshKhilawala:add-examples into 1a1ce5cfeaa2aef5250676abd779543d27e1842b on NeuralEnsemble:master.

[HarshKhilawala]

@apdavison Updated scripts. PTAL!

[HarshKhilawala]

Ready to merge. Suggest additional changes if necessary