Migrate nuget usage from Ripple to Paket

[Paket](https://github.com/fsprojects/Paket) works well as a replacement for Ripple. I've been using it for sometime both at work and on [TikaOnDotnet](https://github.com/KevM/tikaondotnet). 

Might be a good time to migrate away from Rakefile as well. :rabbit: 

