Doesn't support 'mode' parameter

[Matt Cloyd]

I attempted to configure Gistance to use public transit, as follows, but it threw an error.

Gistance.configure do |c|
  c.api_key = 'MY_API_KEY'
  c.mode = 'transit'
  c.transit_mode = 'rail|bus'
  c.transit_routing_preference = 'fewer_transfers'
  c.arrival_time = 1467377100
end

#=> NoMethodError: undefined method `mode=' for Gistance:Module

I'm assuming the gem is out of sync with the latest version of the API. This is supported by the link in the README which points to the Google documentation being redirected to the Distance Matrix homepage.