Implemented `sampling_interval` argument to `Population.record()` for NEST backend
Merge branch 'sampling_interval' of https://github.com/antolikjan/PyNN
bug correction
cleanup
Added support for specifying sampling interval to pyNN.neuron backend.
Added support for specifying sampling interval to pyNN.brian backend.
Merge branch 'master' into sampling_interval
Fixed a bug arising from the merge.
Added sampling_interval handling to mock backend.
Reverting a recently-changed test case.
Corrected some exception constructs to py3

Should hopefully resolve ticket #326

Some more corrections.

Corrected some print statements for py3.

Convert tabs to spaces.

Fixed tab, messed up indentation. Corrected.
Merge pull request #327 from sanjayankur31/326

Corrected some exception constructs in pcsim and nemo backends to work with py3
Merge pull request #328 from apdavison/sampling_interval

Added a `sampling_interval` argument to `Population.record()`