Add updated pip, setuptools, and stevedore

Upgrade pip to 1.4.1 (from ActivePython bundled 0.8.2)
Upgrade setuptools to 2.0.2 (from bundled 0.6)
Upgrade stevedore to 0.13 (from bundled 0.8)
Merge pull request #25 from sot/pip_upgrade

Add updated pip, setuptools, and stevedore