PEP8/pyflakes, simplifications.
'environ' keyword for preprocess.
PEP8 whitespace.
Finish deprecation of PYLEARN2_TRAIN_FILE_NAME.
Fix example with deprecated env var.
Unused import + old environment variable.
PEP8.
Be a bit more careful about os.environ keys.
Add environ argument to higher-level wrappers.
Merge pull request #507 from dwf/environ_argument

Argument to specify additional substitution variables to preprocess()