Removed utils which weren't used within this project.
Remove concept of derived fields, which was never really used.
Removed typed fields. Will re-add after refactoring.
Check for illegal overlap of inherited field names.
Clarify comments.
Removed misnamed and unnecessary 'Struct.__neq__'.
Clean up test cases.
Added parentheses-less use of Field. Added _struct test.
Updated readme.
Create fresh instances of field descriptors for each use.
Add support for tuple decomposition.
Remove check_spec from type.py, tweak comments.
Added type-checked fields as a separate subclass.
Refine equality semantics: field schema must be identical.
Updated examples/point.py.
Change equality semantics again: types must be identical.
Update examples/vector.py.
Changed markdown inline code formatting, added to feature matrix.
Update examples/abstract.py.
Moved unit tests into separate tests/ directory.