Substitute ${..} later during YAML parsing.

Also ensure ensure that obj.yaml_src contains the non-substituted
string.

This fixes https://github.com/lisa-lab/pylearn2/issues/300
Added script to get version of python packages
Environment variable to track repos
Metaclass
Removed class code
Add comments
Add switch to print theano config
Changed metaclass name
Changed metaclass name
Changed file name
Replaced importlib with __import__ so that the script can be run with python < 2.7
Added script to get version of python packages
Environment variable to track repos
Metaclass
Add comments
Add switch to print theano config
Changed metaclass name
Changed file name
adding a unit test for softmax regression tutorial
Removed duplicated function