Tracking issue for all callbacks

[haifeng-jin]

Here is a list of callbacks to be added:

• ModelCheckpoint
• BackupAndRestore
• TensorBoard
• EarlyStopping
• LearningRateScheduler
• ReduceLROnPlateau
• RemoteMonitor
• LambdaCallback
• TerminateOnNaN
• CSVLogger
• ProgbarLogger

[haifeng-jin]

I will take the EarlyStopping for now.

[sampathweb]

I will start with LambdaCallback

[sachinprasadhs]

@haifeng-jin , I think we can close this issue, since every task in the list is completed.

[haifeng-jin]

Yes. Thank you!