1.3.0: Faster Pipe

1. The interface of Operator has Huge breaking.
   • The inputs of Operator.transform are changed. (output_sequence, labels -> output_sequence)
   • The outputs of Operator.transform are changed.
     (output_sequence, output_labels, realigner -> output_sequence, label_aligner)
2. LabelAligner substitutes Realigner.
3. Add lighter Pipe transformation - transform_sequence.
4. Cythonize the elements of edit, including Replacement, ReplacmentGroup, Span and SpanGroup.
5. Cythonize label propagation.
6. Add document for Transformer.

Note: the modification of 1~5 can cut time spending on Pipe transformation by more than 80%.