#3 Add support for *.tar or *.zip (.gz) requirements

On mac you must do `brew install wget` also.  Currently the type is still 'vcs', you might want to create a new type and throw this in there for 'archive' types.
instead of using zip/tar/wget directly, can this just use pip (similar how SetupToolsRequirement.resolve works?)

It would also be nice to parse the VCS repository URL from the requirement URL if it's present (e.g., https://github.com/brad/django-nose/archive/django_1.7.zip#egg=django-nose is clearly a dependency that lives in github.com/brad/django-nose. This won't always be the case, but is likely to be a common scenario).