Replaced Counter in plotgroups for compatibility with Python <2.7
Replaced Counter in plotgroups for compatibility with Python <2.7

mjabri/topographica,Tasignotas/topographica_mirror,ioam/topographica,ioam/topographica,ioam/topographica,Tasignotas/topographica_mirror,Tasignotas/topographica_mirror,mjabri/topographica,mjabri/topographica,ioam/topographica,mjabri/topographica,ioam/topographica,mjabri/topographica,Tasignotas/topographica_mirror,Tasignotas/topographica_mirror