Decide on an output unit, and make output available in get_value

[jmframe]

Short description explaining the high-level reason for the new issue. We need one output for this model. We can provide it in units of either: ['mm', 'ft3 s-1', 'm3 s-1]. So decide on that, and then make it available through the get_value. And that requires associating the chosed output unit with 'land_surface_water__runoff_volume_flux'.

Current behavior

Nothing currently associated with 'land_surface_water__runoff_volume_flux'.

Expected behavior

_var_name_units_map = {'land_surface_water__runoff_volume_flux':['streamflow_cfs','ft3 s-1'],  ... etc.}  

def scale_output(self):  
    ...  
    self._values['land_surface_water__runoff_volume_flux'] = self.streamflow_cms * (1/35.314)  
    ...OR...  
    self.land_surface_water__runoff_volume_flux = self.streamflow_cms * (1/35.314)  

etc.

[jmframe]

Fixed by PR #12