MAINT: remove our solve_triangular

No longer needed, since we depend on scipy >= 0.9
MAINT: commit generated code
MAINT: scipy 0.10 and 0.11

linalg.solve_triangular does not have a check_finite keyword argument
Merge pull request #2931 from GaelVaroquaux/rm_solve_triangular

[MRG]: MAINT: remove our solve_triangular