MAINT: attempt debugging some code that behaves differently on different LAPACKs
MAINT: disable a test that involves singular matrices and which seems to not be stable across different LAPACKs
Merge pull request #2768 from argriffing/lax-fractional-matrix-power-singularity

TST: mark a fractional_matrix_power test as knownfail
REL: set version of master to 0.14.0-dev, add 0.14.0 release notes.