Update release notes.

Merge pull request tensorflow#29548 from tensorflow/bananabowl-patch-2

Copy cl/250062993

Merge pull request tensorflow#29521 from goldiegadde/ggadde-cp2

Revert "Fix an important performance regression for LSTM and GRU in t…

Merge pull request tensorflow#28973 from bananabowl/cherrypicks_NL20I

Two cherrypicks

Merge pull request tensorflow#27959 from tensorflow/update-release-no…

…tes-version

Update header on release notes

Merge pull request tensorflow#27699 from yongtang:27497-ragged-axis

PiperOrigin-RevId: 244173513

Merge pull request tensorflow#26373 from goldiegadde/cherrypicks_MQMPF

Disable bincount_op_test on windows gpu.

Merge pull request tensorflow#26101 from gunan/r1.13

Bump TF version to 1.13.1

Merge pull request tensorflow#25769 from aselle/cp-20190214b

Fix regression in XLA in TensorFlow 1.13 RC0, RC1

Merge pull request tensorflow#25562 from tensorflow/aaroey-1.13-relea…

…se-note

Update RELEASE.md