1.4.1 Release Updates (tensorflow#15200)

Initial add of docs for Tensorflow on Mobile. (tensorflow#14161)

PiperOrigin-RevId: 173980290

Add known Dataset issue to RELEASE.md. (tensorflow#13870)

Adding info about issue using Unicode strings with Datasets.

Merge pull request tensorflow#13617 from case540/add_authors_to_notes…

…_1_4

Add contributing authors to 1.4 Release notes.

Merge pull request tensorflow#13300 from av8ramit/1.3.1

GitHub only 1.3.1 release.

Merge pull request tensorflow#12342 from jart/r1.3-tensorboard-notes

Add TensorBoard to 1.3 release notes

Merge pull request tensorflow#12013 from tfboyd/grappler_off_branch

Make layout optimizer_test manual due to Grappler being off in the r1.3 branch.

Merge pull request tensorflow#11794 from av8ramit/update_version

Update version to rc1.

Merge pull request tensorflow#11616 from av8ramit/1.3rc0-relnotes

Updating the RELNOTES for 1.3.0rc0.

Merge pull request tensorflow#11156 from av8ramit/1.2.1

Updating release.md.