Uniform distribution can be integer
Functions for loading tests in other backends
Use regex to make test search configurable.
Fixes to `utils.testing` import functions

- Added `utils.compat` with helper functions
  for proper type checking
- Simplified many type checks throughout the code
- Documentation changes to test import functions
Test module search now uses `os.walk`

- also fixed an unused variable flake8 warning
Python 3.4 support

- Python 3.4 now tested when running tox
- Travis-CI testing for 3.4 will be enabled when available
Maintain hierarchy in api, enforce with

 - Model (now Network) is recursively structured.
 - 'with' is required.
 - Fixed a test which occassionally failed due to floating point
   comparisons
 - NengoObject base class for simplifying __hash__, __str__, etc...
 - A bit of general cleanup with string quotes and specifiers
Improved test_builder
Faster method for testing notebook examples

Instead of starting up an IPython kernel and executing cells,
we just convert the whole notebook to a Python script
and exec it.

Other minor changes:
- Moved some things in test_examples to utils.ipython
  - Should now be easy to generate Python scripts for docs
- Changed requirements-test, and pyzmq is no longer necessary
  (but jinja2 and pygments are)