Convert to Tensorboard logs

[stephenpardy]

Is your enhancement request related to a problem? Please describe
Tensorboard is a standard way of visualizing and tracking neural network model experiments. Rubicon logs are often logging the same information in a different format.

Describe the solution you'd like
Provide a backend to Rubicon that allows users to save to Tensorboard.

Describe alternatives you've considered
Could look to make Rubicon visualizations on par with Tensorboard.

Additional context
N/A

[ryanSoley]

I think we could at the very least make a backend that logs metrics as custom tensorboard scalars

https://www.tensorflow.org/tensorboard/scalars_and_keras#logging_custom_scalars