TadGAN `batch_size` cannot be changed

[sarahmish]

Orion version 0.3.2 does not support TadGAN to change batch_size.

What needs to be changed

Orion/orion/primitives/tadgan.py

Line 31 in 192f45a

alpha = K.random_uniform((64, 1, 1))

Allow a variable input

alpha = K.random_uniform((batch_size, 1, 1))