Removed EnsembleNeuronTypeParam.

This was only necessary when we wanted to probe neuron stuff on the
ensemble. Now that we use the neurons object, this was unnecessary.
Added more validation to Connections

-no connections to Direct neurons (Issue #463)
-no functions on passthrough nodes (Issue #428/#485)
Remove networkx dependency in setup.py

And bump up the numpy version to 1.6.
Force setuptools

If we can be assured that we're using setuptools,
we can make setup.py a lot more effective. This should be possible,
as the ez_setup.py script (now included) should be able to download
and install setuptools on all OSes.

A few nice things if we can rely on setuptools
- simpler setup.py
- use find_packages function instead of having to edit setup.py
  when we add a new package
- extras_require for a one-command install of Nengo and extras
Better testing in setup.py

Now:
- `python setup.py test` launches py.test,
  which is usually what people want.
- tox is still accessible with `python setup.py tox`
- Both can have command-line arguments passed in using the -a switch
  (or the long --pytest-args or --tox-args switches);
  e.g., `python setup.py test -a "-n 4"` is equivalent to
  `py.test -n 4` and `python setup.py tox -a "-epy34 -- -n 4"`
  is equivalent to `tox -epy34 -- -n 4`
Removed makefiles in docs

The preferred ways to build documentation are

1. python setup.py build_sphinx, or just ./setup.py build_sphinx
   (See python setup.py build_sphinx --help for options)
2. Invoke sphinx-build directly; e.g., sphinx-build docs html
   (See sphinx-build --help for options)
Use semantic versioning.

See the nengo/version.py docstring for more details.
Simplified requirements files

Setuptools allows extra_requires with `req[extra]` syntax.
Also, matplotlib 1.4 has an improved setup.py that can
handle being installed simultaneously with numpy,
so no need to install from git anymore!
Fix circular convolution radius
Added test of magnitude control
Fixed up some test plots.

- Fixes #345.
Add simple text based progress bar implementation.
Adjust progress bar width to terminal width.
Reorganize progress bar code.
Add ETA and seconds_passed to progress bar.
Layout CmdProgress.
Time based update interval.
Extract Progress class.
Only show progress bar for long simulations.
Simplify code with ProgressControl.