Changed setup.py to use sugar3 for Gtk3 migration.

Added executable permissions to setup.py.
Converted readme to actual markdown from html.

Adjustments to organization and layout, and content of readme.

Fixed build instruction redundancy.

Cleaned up file descriptions.

Added sections for Gtk and Multi-Lingual development.

Began integrating complete example.
Added HTML copy of the readme.
Adjusted activity.info for example activity.

Added empty icon SVG place-holder.
Adjusted readme regarding icon placeholder.
Filled out example activity with some basic Gtk widgets.
Updated readme to reflect Gtk3 instructions.

Updated the html readme that accompanies the markdown.