Add plugin and compat tests for tensorboard-notf

[orionr]

Continuation of #1663

This adds plug and TensorFlow compat tests both locally running and in Travis CI.

cc @nfelt, @lanpa

All the tests can be run with

bazel test //tensorboard/compat/proto:proto_test --test_output=errors
bazel test //tensorboard/compat/tensorflow_stub:gfile_test --test_output=errors
bazel test //tensorboard/compat/tensorflow_stub:gfile_s3_test --test_output=errors
bazel test //tensorboard/plugins/audio:audio_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/custom_scalar:custom_scalars_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/distribution:distributions_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/graph:graphs_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/histogram:histograms_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/image:images_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/pr_curve:pr_curves_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/projector:projector_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/scalar:scalars_plugin_notf_test --test_output=errors
bazel test //tensorboard/plugins/text:text_plugin_notf_test --test_output=errors

[wchargin]

If I understand correctly, only the second commit in this pull request
(“Add plugin and compat tests for tensorboard-notf target”) is intended
to be reviewed, yes?

[orionr]

@wchargin that's correct. I can remove the other if we don't mind test failures right now. What would you prefer? Thank you.

[wchargin]

Keeping the commits as-is is fine; once #1663 merges, you can update
this PR.

I don’t have too much context here, but the second commit seems pretty
unobjectionable, so I think that this is basically blocked on #1663.

[orionr]

This has been rebased on top of master and should be ready for review. Thanks, @nfelt and @wchargin!

[orionr]

Rebased.

[orionr]

@wchargin any interest in reviewing and landing this? @nfelt also feel free to comment if you have concerns.

[nfelt]

This is not the right long-term solution, but for now it improves test coverage, so we can merge once the projector tests are cleaned up per comment below.

Can you also merge in the latest changes from master?

[orionr]

Need to upgrade bazel to test locally, but just rebased and pushed changes to match the review. Let me know your thoughts and thanks.

[orionr]

This should be ready to merge @nfelt and @wchargin. Thanks.

[nfelt]

Thanks for the updates!