Fix bug in codeobject creation
Add a test and a simple performance benchmark for spikeque
Refactor SpikeQueue, put indices into their own class and implement
access to synaptic state variables.
Implement the new syntax for multiple pathways.
Fix unit checking for synaptic variables and treat delay as a synaptic variable.
Allow S.delay as a shortcut to S.pre.delay
Adapt test to refactored SpikeQueue
First implementation of three-dimensional indexing
Add convenience methods to add connections to a Synapses object