Added convenience function time_dependent to topo/__init__.py
Added convenience function time_dependent to topo/__init__.py

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