Move mode and units into post body for distance matrix

[leenyburger]

Closes ENG-660.

Will need to be tested once comments on that issue are resolved.

[leenyburger]

This issue illuminated an issue on the API side.
This issue is solved by this PR -> units and mode are now in the post request body. The API change does not block the CLI release.

Test Criteria

• Send the following cli command.

echo "Washington DC" > /tmp/origins.txt
echo "New York" > /tmp/dests.txt

• Confirm that units and mode are in the POST request body not the param, i.e. they are recieved.
• Confirm that

geocodio distance-matrix --origins /tmp/origins.txt --destinations /tmp/dests.txt --mode straightline --units km
 Origin: Washington DC To New York
Distance           364.7 km (226.6 miles)
Duration           284 minutes

returns km as primary

• Confirm that

geocodio distance-matrix --origins /tmp/origins.txt --destinations /tmp/dests.txt --mode straightline --units miles
 Origin: Washington DC To New York
Distance           364.7 km (226.6 miles)
Duration           284 minutes

returns miles as primary

• Confirm that geocodio distance-matrix --origins /tmp/origins.txt --destinations /tmp/dests.txt --mode straightline and geocodio distance-matrix --origins /tmp/origins.txt --destinations /tmp/dests.txt --mode driving do not return the same thing