Add py-rwt 2.15.1

RWT (Run With This) provides on-demand dependency resolution.

• Allows declaration of dependencies at runtime. - Downloads missing dependencies and makes their packages available for import.
• Installs packages to a special staging location such that they're not installed after the process exits.
• Relies on pip to cache downloads of such packages for reuse.
• Supersedes installed packages when required.
• Relies on packages already satisfied.
• Re-uses the pip tool chain for package installation and pkg_resources for working set management.

WWW: https://pypi.python.org/pypi/rwt
WWW: https://github.com/jaraco/rwt