Filter deprecated packages from the displayed list

* Add DEPRECATED_PACKAGES list of package names
* Add not_deprecated function

Fixes #28. Fixes #39.
Use set for DEPRECATED_PACKAGES instead of list
Add paragraph about deprecated packages
Move filter into remove_irrelevant_packages
Merge pull request #42 from Ian-Foote/deprecated_packages

Filter deprecated packages from the displayed list
Replace set literal with set() for python 2.6