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Some audio formats like `gsm` does not have valid frame numbers when opened. But `libsox` can properly handle these audios, so checking if `length > 0` is not necessary and too strict.

After a9f5e7229 was merged into upstream pytorch the passing of
references within torch c extension functions is no longer allowed. This
just removes the reference and passes by value instead.
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>

* Distinguish get_encodinginfo for Tensor I/O and save output

* Isolate get_tensor_encodinginfo so as not to use the same helper function

Co-authored-by: Prabhat Roy <prabhatroy@fb.com>

* Support file-like object in save func

* Disable CircleCI cache for TP artifacts for cleaner build

* Separate sox list format function for read and write

* Guard MP3 smoke test

* Add sox_utils module

* Make init/shutdown thread safe

* Add sox effects implementation

* Add test for sox effects

* Update docstrings and add examples

This is a part of PRs to add new "sox_io" backend. #726 and depends on #718, #728 and #731.

This PR adds `save` function to "sox_io" backend, which can save Tensor to a file with the following audio formats;
 - `wav`
 - `mp3`
 - `flac`
 - `ogg/vorbis`

This is a part of PRs to add new "sox_io" backend. #726 and depends on #718 and #728 .

This PR adds `load` function to "sox_io" backend, which is  tested on the following audio formats;
 - `wav`
 - `mp3`
 - `flac`
 - `ogg/vorbis` *

By default, "sox_io" backend returns Tensor with `float32` dtype and the shape of `[channel, time]`. The samples are normalized to fit in the range of `[-1.0, 1.0]`.

Unlike existing "sox" backend, the new `load` function can handle WAV file natively, when the input format is WAV with integer type, (such as 32-bit signed integer, 16-bit signed integer and 8-bit unsigned integer) by providing `normalize=False`, this function can return integer Tensor, where the samples are expressed within the whole range of the corresponding dtype, that is, `int32` tensor for `32-bit PCM`, `int16` for `16-bit PCM` and `uint8` for `8-bit PCM`. This behavior follows [scipy.io.wavfile.read](https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.wavfile.read.html). `normalize` parameter has no effect for other formats and the load function always return normalized value with `float32` Tensor.

__* Note__ The current binary distribution of torchaudio does not contain `ogg/vorbis` and `opus` codecs. To handle these files, one needs to build torchaudio from the source with proper codecs in the system.

__Note 2__ Since this PR, `scipy` becomes required module for running test.