Added group_variable_set template because reset is hardcoded to
_spikespace now, fixed reset to not use _spikes
Fixed SpikeMonitor to use _spikespace
Fixed RateMonitor to use _spikespace
Removed all reference to _spikes Variable
Remove a TODO comment that no longer applies
Merge pull request #102 from brian-team/no_more_spikes

No more _spikes attribute (replaced by _spikespace which was introduced with #97)