make pylearn2 importable from python 2.6.

This is needed to generate the doc on the web site, as it is python 2.6 that is available.
Fix doc syntax
Remove use of python 2.7 and up fct.
import python 2.6 version of OrderedDict when needed.
Add numpydoc as sphinx extension.
add pyyaml and argsparse as dependency.
fix pep8
remove automodule on module that don't exist anymore.
Fix some doc syntax error.