Replaced all Transform,Filter,Decoder,Encoder with simple operations
Cleaning up comments
Added the skipped tests back in
attempting to add voltages probe
Fixed issue with neuron.voltage probe signal

- Wasn't being set with correct dimensions.
- Fixed __str__ function for simulator.ProdUpdate class.
- Updated comment regarding redefinition of signal dimensionality.
voltage probe working and demo'd

- Fixed incorrect asarray call
Merge branch 'master' of https://github.com/ctn-waterloo/nengo into peter-examples
Converted oscillator example to ipython notebook
Converted single neuron example to ipython notebook