Added an abstractproperty sym_wt to HeckeModuleElement.
Modified the method __getitem__ of SymmetricWeightGenericElement.
Added method is_eigen_form to HeckeModule.
Modified method normalize.
Added function degree2_modular_forms_ring_level1_gens.
Added test/data.
Added tests for vector valued differential operator.
Modified _rankin_cohen_bracket_func.
Merge branch 'master' of github.com:stakemori/degree2
Removed some comments.
Added a module for the space of vector valued SFMs.
Added rankin_cohen_triple_det_sym2.
minor fix.
Modfied method __mul__ and __getitem__.
Fixed linearly_indep_tuples.
Modfied _hecke_op_vector_vld.