Move module docstring to the top of the file
Move documentation to doc/ subdirectory
Remove superfluous toctree directive
Change to automodule and use source order
Move property documentation from __init__() to the properties
Change display of return type
Shorter summary of endian-ness
Remove names of return values from docs
Kill open()
Re-order functions

See #57.
Re-order methods within SoundFile

See #57.
Use the __init__() docstring as class documentation
Add requirements file for Sphinx

This is needed for readthedocs.org because the current version doesn't
yet include the napoleon extension (it will be included in version 1.3).