Skip test for mode='x' in Python < 3.3

Before, it was only skipped for Python 2.x
Use __array_interface__ instead of array.ctypes.data

Currently, PyPy doesn't support latter.
Tests: change calculation for PyPy compatibility

Multiplying an int16 array with 2**16 didn't upgrade the dtype to int32.
Enable "python setup.py test"
Get Sphinx release number from Git (if available)
Remove pysoundfile from requirements
Merge pull request #90 from nils-werner/requirements

Remove pysoundfile from requirements
Merge pull request #81 from bastibe/skip-x

Skip test for mode='x' in Python < 3.3
Merge pull request #85 from bastibe/pypy

Compatibility with PyPy
Delete requirements.txt

The actual requirements are specified in setup.py, these additional
requirements just add confusion.
See #82.
Remove SoundFile.frames attribute

There is already a more idiomatic way to get that information: len().

See #69.
Add MANIFEST.in

This adds the license file and everything from doc/ and tests/ to the
"sdist" tarball (which eventually ends up on PyPI).
See #80.
Merge pull request #82 from bastibe/issue-82

Change (or remove) requirements.txt
Merge pull request #69 from bastibe/issue-69

Remove either frames property or __len__() from SoundFile
Merge pull request #80 from bastibe/issue-80

Add MANIFEST.in
Add SoundFile.tell()

See #44.
Change PDF documentclass from 'manual' to 'howto'

See #93.
Merge pull request #93 from bastibe/issue-93

More compact PDF documentation
Allow mode='x' even for Python < 3.3

The built-in open() function isn't used anymore.
The function os.path.isfile() is used to check if a file exists already.
For mode 'w+', an existing file is first opened in write-only mode to
make sure it is truncated. Afterwards it is re-opened in read/write
mode.
Merge pull request #94 from bastibe/emulate-x

Allow mode='x' even for Python < 3.3