Better error messages

[turian]

It's natural to try plugging in a scalar when building a new synth. This leads to cryptic errors, e.g.

  File "/opt/miniconda3/lib/python3.9/site-packages/torchsynth/module.py", line 437, in ramp
    start = self.seconds_to_samples(start).unsqueeze(1)
IndexError: Dimension out of range (expected to be in range of [-1, 0], but got 1)

It would be more friendly if there were a global thing that trapped all forwards, checked the parameters, and made sure they are all tensors with tensor.shape[0] == batch_size, otherwise an informative error message is printed.