Base call to SoX uses shell=True in subprocess call

[rabitt]

Filenames with wildcards have always behaved inconsistently with pysox. Looking into this more closely, found that - the SoX command arguments being passed to the shell rather than to the binary directly.

Thanks @jongwook for finding the source!

[lostanlen]

The LoCs at stake are:

in sox
https://github.com/rabitt/pysox/blob/master/sox/core.py#L51

in soxi
https://github.com/rabitt/pysox/blob/master/sox/core.py#L128

[rabitt]

@lostanlen unfortunately it's a change that creates cascading changes all over the library. Working on it now.