Simplify the docs by merging the 'default' and 'simple' sections, since they are the same.
Update Geocoding docs to show where 'client' comes from.

This streamline things if you arrive at this page first, you don't have
to flip back and forth between here and the README / Getting Started
page to quickly have a complete example to work from.
Remove some stray whitespace from the docs.
Numerous improvements to Geocoding docs. See commit details

* Code snippets are now tagged as JavaScript or JSON, for better syntax highlighting.

* The Batch geocoding docs were updated to show more realistic
  async-style use, where the the results are processed inside the
  authentication callback.

* The parameters passed to the authenticate callback are documented now.

* The optional options for batch geocoding are documented now.

* An example results structure for Batch geocoding is documented.

* The official ArcGIS REST APIs are linked to and referenced as the
   official documentation for the related API calls.
Merge pull request #63 from markstos/improve-geocoder-docs

Improve geocoder docs