Support for data formats

By default your data will be stored as JSON in Couchbase. You can
also change the format to "pickle" which will use the pickle module
on your object, or "plain" which won't modify your data at all.

Getting the data is transparent, it will do the convesion back to
the original data for you.

This commit also cleans up the code a bit, when using GCC for
compilations there shouldn't be any warnings any more.
Move code into sub-directory

The module is now called couchbase. Import the main class with
`from couchbase import Couchbase`.
Rename files

The files now have better names. The central Cython pyx file
is now called couchbase.pyx. The declarations from libcouchbase
are now in a file called libcouchbase.pxd.
Another renaming

couchbase.pyx was renamed to libcouchbase.pyx and includes
additional *.pyx files.

Some docstrings were also added.
Docstring fixes
Add auto-generated API docs
Adding tests