v0.3

• Processes now support multiple inputs and multiple output commodities.
• As a consequence plot() now plots commodity balance by processes, not input commodities.
• urbs now supports input files with only a single site; simply delete all entries from the ‘Transmission’ spreadsheet and only use a single site name throughout your input.
• Moved hard-coded ‘Global CO2 limit’ constraint to dedicated “Hacks” spreadsheet, while the constraint is add_hacks().
• More docstrings and comments in the main file urbs.py.