Adding entity field search
Updated README.md

* Removed note about changing to require API key starting 1. December
2012 as that is long past.
* Moved documentation URL into the list of instructions for getting
started and added the non-io-docs URL too.
Updated README.md

* Removed "Register" line as that is also the first step of the list of
instructions for getting started.
Merge pull request #1 from LarsJNielsen/master

Adding entity field search