Modernize development environment and fix custom policies with no ip_range argument

First commit modernizes the dev-environment by using a simple gemspec instead of jeweler, using markdown (with ruby syntax highlighting) instead of rdoc for the README and bundler for gem-management.

Second commit fixes custom policies without ip_range argument which would result in "Malformed Policy" error.

If you don't wish to update your development environment you could also just cherry pick the ip_range fix.