Add two tests showing problems with scalar delays (currently failing).
Make the C++ SpikeQueue correctly work with scalar delays
Use the source clock, not the synapses clock, when converting delays to integers
Raise a warning when using different dts for source, target, synapes. This can lead to unexpected results since a pre(post) pathway is always run on the source(target) clock. In particular, delays are rounded to the pathway's clock.
Merge pull request #352 from brian-team/synapse_delay_fixes

Synapse delay fixes