Introduce auto-matrix indices
removed useless code
fixing error
GammaMatrix objects are now commutative
fixed typos and minor errors
changing commutation group in test
added ``_get_lines`` and ``simplify_lines``
fixed bug in ``_join_lines``
fixed bug in ``_get_lines``
finished implementing ``simplify_lines``
Simplify now returns a delta function on spinor indices when final rank was previously zero
add auto-matrix deltas if needed in TensAdd. delta and metric are now auto-matrix tensors
fixed ``_kahane_simplify``, ``_trace_single_line``
modified ``gamma_trace``; added tests and documentation
faster ``contract_metric``; added ``get_lines``
fixed bug in ``_simplify_single_line``; modified ``simplify_gpgp``
merged master
Indices renamed
Merge pull request #2467 from Upabjojr/tensor_matrix

Introduce auto-matrix indices