Simplified example

(Caution: UNTESTED!)
The example made little sense. 

The Undo stack was used to run the commands, not just undo them. Renamed.

The commands had names, for no reason. They are now added directly to the stack.
The stack was edited (popped) while it was being iterated. The cmd variable was unused. Replaced with simple iterator.

The stack should be undone in reverse order. reversed() added.

The comments had grammatical errors. Corrected.
Fixed PEP-8 discrepancy in Bridge pattern
Fixed PEP-8 discrepancy in Pool pattern
Fixed PEP-8 discrepancy in Strategy pattern
Fixed PEP-8 discrepancy in Prototype pattern
Merge branch 'pep8_pool' of https://github.com/jcdenton/python-patterns into jcdenton-pep8_pool
Merge branch 'pep8_strategy' of https://github.com/jcdenton/python-patterns into jcdenton-pep8_strategy
Merge branch 'pep8_prototype' of https://github.com/jcdenton/python-patterns into jcdenton-pep8_prototype
Merge branch 'pep8_bridge' of https://github.com/jcdenton/python-patterns into jcdenton-pep8_bridge
Simplified chain comparisons.
Added foo.txt for command.py script.
Small pep8 correction.
Removed redundant parentheses.
Few minor changes.
Minor pep8 correction of the docstring.
Minor pep8 correction of the docstring.
Removed trailing spaces on numerous lines.
Minor pep8 correction of the docstring.
Renamed element 'type' to 'Type'.
Some minor changes