Documentation doesn't build on RTD for core functionality

[pseeth]

Getting the following errors for building documentation.

WARNING: autodoc: failed to import module u'core' from module u'scaper'; the following exception was raised:
No module named soundfile
WARNING: autodoc: failed to import module u'core.Scaper' from module u'scaper'; the following exception was raised:
No module named soundfile

WARNING: autodoc: failed to import module u'core' from module u'scaper'; the following exception was raised:
No module named soundfile
WARNING: autodoc: failed to import module u'core.Scaper' from module u'scaper'; the following exception was raised:
No module named soundfile
/home/docs/checkouts/readthedocs.org/user_builds/scaper/checkouts/stable/docs/tutorial.rst:343: WARNING: Error in "code-block" directive:
1 argument(s) required, 0 supplied.

Self-assigning and will PR with a fix.

[justinsalamon]

Fixed via #81