= TODO

* user defined sorting
* add field compression
* Fix highlighting to work for compressed fields
* Fix highlighting to work for external fields
* Add Ferret::Index::Index
* Fix:
> Working Query:  field1:value1 AND NOT field2:value2
> Failing Query:    field1:value1 AND ( NOT field2:value2 )

= Done
* Add string Sort descripter
* fix memory bug
* add MultiReader interface
* add lexicographical sort (byte sort)
* Add highlighting
