Direct first-time users to Topographica's downloads page.

The ioam/topographica downloads page only has old source tar.gz packages, so unless there's a plan to alter the ioam/topographica downloads page, linking to Topographica's downloads page seems to make more sense.
Fixed a typo.
Fixed to show how to get new random pattern
Removed out-of-date reference to subproject files
Added dim_fraction support for image inputs
Fixed outdated references to dataviews.odict
Fixed broken import in Topographica IPython extension
Updated StorageHook to work with FeatureMapper return type ViewGroup
Fixed SheetView generation for sheet and projection activities
Updated dataviews and featuremapper submodule references
Updated dataviews and featuremapper submodule references
Updated boundingregion and sheetcoords imports from dataviews
Updated submodule references
Updated imagen submodule reference
Updated Topographica to new shared Sphinx documentation system
Made topo/hardware/playerrobot.py importable if import fails
Updated param, dataviews and featuremapper submodule references
Fixed dataview object titles
Updated dataviews, featuremapper and param submodule references
Moved ProgressBar and RunProgress to dataviews.ipython.widgets