Add support for visualizing chrome trace files in tb_plugin from S3 URLs

[chauhang]

For chrome trace files in S3 bucket, the tb_plugin UI gets stuck in spinning wheel to load the files and nothing gets displayed. Add support for visualizing the traces from S3 URLs for the Profiler plugin, similar to how one can view the main tensorboard runs in the rest of the tensorboard UI.

[guotuofeng]

duplicated item with #177