doc/intro.rst: tweak wording
splat/data.py: no need for AudioFile to be a Sequence

Now that there is the `get_bytearray' method, there is no
need to implement a Sequence interface any more.
splat/data.py: remove AudioFile class altogether

Use audio file handler functions to create a Fragment
instead of unnecessary audio file factory.
splat/data.py: rename Fragment.save() and add file format handlers

* rename Fragment.save_to_file -> Fragment.save
* add `fmt' argument to specify the output file format (i.e. 'wav')
* use file name extension by default if no format specified
* add save_wav handler and dictionary for all file formats
* pass extra arguments and kw from Fragment.save to the handler
* update docs accordingly
update references to Fragment.save + fix benchmark.py
_splat.c: add 8-bit support in _Fragment.as_bytes
test.py: fix MD5 of test_sine to match correct output

The initial Generator levels were changed from 1.0 to 0.0
in d3c6f3c1b668 (dB instead of linear gain) so the
SineGenerator output has changed and is now correct.
Fragment: add default number of channels and sample rate

* _splat.Fragment: add keywords and default values for
  channels (2) and sample rate (48000)
* splat/data.py: update docstring accordingly
test.py: use new Fragment keywords (duration)
doc/index.rst: fix HTML and LaTex conflicts

* add quick intro only for HTML output
* rename remaining Geomusic -> Splat
* tidy-up
review and fix typos in documentation
build-0003