Fix the link to the tests in the README.

Fixes #2.
Make the README easier to understand, and get rid of the RekordType.
Test with different parameters to ensure the code remains flexible.
The Rekord constructor should be private.
Remove an unnecessary temporary variable.
Move rekord construction to the rekord types.
Move Box to the Rekords test objects class.
Rename "key" to "originalKey" and "actualKey" to "key".
Move the original key storage to the key itself.
Rekords should specify their keys.
Handle the `originalKeys` stuff in the Properties class internally.
Add the rekord to the Sandvich type in the README.