Update docs on proper usage of asPromise()

[DaddyWarbucks]

In reference to #89

I left the syntax in the example for promises very simple. The asPromise() could arguably be on the next line, like the following:

googleMapsClient.geocode({address: '1600 Amphitheatre Parkway, Mountain View, CA'})
  .asPromise()
  .then((response) => {
    console.log(response.json.results);
  })
  .catch((err) => {
    console.log(err);
  });

But, I wanted people to see that it is chained onto the googleMapsClient directly and thought the code in the actual PR was more clear.

I also noticed that the second code example in the docs does not have the js declaration within the markdown to highlight it is javascript. "```js" would syntax highlight the following

// Geocode an address.
googleMapsClient.geocode({
  address: '1600 Amphitheatre Parkway, Mountain View, CA'
}, function(err, response) {
  if (!err) {
    console.log(response.json.results);
  }
});

I wasn't sure if that was done on purpose, but I would be happy to fix that as well.

• Beau

[stephenmcd]

I wasn't sure if that was done on purpose, but I would be happy to fix that as well.

I think it was accidentally omitted, please go for it.

[stephenmcd]

Thanks a lot!