upgraded tensorflow and handled torch cuda

[Sathishsathi]

This PR includes following changes:

• Upgraded tensorflow package
• Changes made in hparams to adapt the new version of tensorflow
• hparams changes includes removing of contrib from tensorfow (since it is deprecated in new version) and converted the params as dict
• To train the tacotron locally where cuda is not available, a condition is added. If cuda is not available, torch will executed without cuda. Please find the code for reference.
• Tested locally and it is working fine. Since it is handled with if condition, it will not affect the existing flow