Added info to crime incidents page

Added a few things to the crime incidents page:

- UCR code breakdown to make it easier for people to get started
- A sample geometry call
- links to the ArcGIS REST API documentation so that devs can learn even more

Also fixed a typo in the README.

At some point I'd like to work on more query examples just to show everything that the API can give you so that developers don't experience the same frustrations that I did at first.

Thx!