Fix doc syntax
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.
Merge pull request #311 from nouiz/import_py26

Import py26
Fix typo in validation.
Use math.log instead of np.log for Python longs.
Fix the masking behaviour.
Added function to sample masks from the distribution.
Per example switch for sampled_dropout_average.
More error-checking in exhaustive_dropout_average.
Properly initialize input_scales in exhaustive_dropout_average.
Special case the zero mask in masked_fprop.
Get rid of the np.all() special case that is causing a test failure.