Updates to neovi module documentation, including adding details to NeoDevice.get_settings.
Tweaks to Sphinx conf.py.

Updated neodevice module documentation, particularly the set_settings methods.
Switched can module documentation to just include source for now.
Spec module documentation now points to an example of how to use a spec.
Added requirements file.
Update hgignore file.

Minor code and documentation updates/fixes.
Vehicle spec identifiers now use enums for IO type and value type.
Vehicle spec signals now use an enum for signal type.

Added a README with basic info.
Changed the documentation config to avoid explicitly listing __init__ methods and to order module members as they appear in the source.
Moved array_equal into structures.py to avoid duplicating code.
More documentation.