Added tip about Inkscape
Merge branch 'master' of github.com:ioam/topographica
Cleaned up output directory handling, in part for Jenkins support.  Moved default output path code out of topo/__init__ and into topo/misc/commandline.py, so that it can be overridden by setting param.normalize_path.prefix in .topographicarc or through a new option -o <path>.  Made topo/tests/test_script respect param.normalize_path.prefix and avoid creating an output directory when loaded, postponing that until the functions are actually run, to avoid creating spurious output from nose.