Use "real examples" for testing

[mstimberg]

Have a look at Brian2s examples and see which could be in principle supported by our LEMS/NeuroML export. If there's only a small functionality that is missing, then it might be worth implementing it. It would be great if at the end we'd have a few examples that do something non-trivial. With support for synapses (#6), I think we should be able to run e.g. examples/synapses/licklider.py (not 100% sure about the noise, though, you might have to manually replace "xi" by something like sqrt(dt) * normal() (or whatever LEMS uses for randn)).
With support for PoissonGroup (#8), also examples/synapses/STDP.py should work.

[pgleeson]

Another option might be to construct a new example to add to the standard Brian examples that does something interesting but that you know is fully supported in the NML2 export. That example can be updated as the features in the export are expanded.