Fixed neuron model under Windows
Suppress invalid value warning in rates
Minor fixes to probes.

- Probes can now take **kwargs to pass to Connection
  (for example `decoder_solver`)
- Probe sample rate now defaults to simulator `dt`
Check nodes for matrix output.

Fixes #267.
Check Node output when `size_out` is provided.
implemented simple connection slicing
Moved Neurons and ObjSlice to objects.py

- Also patched some odd issues with deepcopying np.sin on Python3
made Node dimensions mandatory

this was required for EnsembleArray slicing

also added some more tests
Simplified Connection checks
Connection.transform is now unpadded

The padded version is available as Connection.transform_full
Quick patch for test_context.test_with

- Not a permanent thing!
Ensure builder does not modify transform_full

By making it have a handle to a copy.

Also updated the Connection docstring.
add *.class to gitignore
New configuration system

Mostly for backend-specific parameters.
Made config dict a WeakRefDictionary

(see http://nbviewer.ipython.org/urls/gist.github.com/ChrisBeaumont/5758381/raw/descriptor_writeup.ipynb
for reasoning)
Changed to decorator syntax
Made config system more Pythonic

- Also added examples to docstrings
Class hierarchies handled in Config system
Implemented remove_passthrough_nodes

This can be called by builders to make the model faster.
It removes Nodes with `output is None`.
Added labels to EnsembleArray