Add documentation.
Replace parsed segment string with segment field values.
Check only for the empty string in int_empty_zero.
Support Python 2 str objects, alleviating the need for Python 2 clients to use the future library or unicode objects.
Improve SegmentField and SegmentDefinition validation.
Fix #4: Implement segment field access by name.
Fix #4: Implement segment field access by name.
Update the version number and documentation for version 1.2.