Bug fix: Uninstall old packages before installing new ones (issue #7)

See issue #7 on GitHub:
  https://github.com/paylogic/pip-accel/issues/7
Bug fix: Avoid repeating output when running pip multiple times (issue #9)

Issue #9 on GitHub:
  https://github.com/paylogic/pip-accel/issues/9
Improve user feedback (report retry count)
Silence the output of "python setup.py bdist_dumb"
Initial support for installing system dependencies
Extract predefined dependencies to configuration file
Reformat README.rst to make it nicer to read as source (also improves diffs)
Document the new system package dependency tracking
Fix tests, add file header, add makefile