docstrings.

--HG--
branch : pure-cffi
docstrings and better naming.

--HG--
branch : pure-cffi
review FIXME.

--HG--
branch : pure-cffi
change pyrana.format.find_stream semantics

to something actually useful and less trivial.

--HG--
branch : pure-cffi
Fixed a bug in make_enum utility to parse nested enum included from other header files

--HG--
branch : pure-cffi
Replaced the self.__class__.<class_variable> notation with <class_name>.<class_variable>

--HG--
branch : pure-cffi
add AVPacket support in cffi.

--HG--
branch : pure-cffi
first sketch of the _read_pkt demuxer workhorse

--HG--
branch : pure-cffi
Merge ../pyrana