Process Atom feed

 - Added Atom feed process
 - Added Atom response extension
 - Call atom response in formatter extensions
 - Added /atom to nancy module
 - this snow.config generates an atom feed rather than rss, but could just as easily do both.
 - atom feed validates on validator.w3.org/feed
Merge pull request #98 from sgrassie/atom

Added Atom feed processor
Better use of Costura, allows for mono compatibility.
merged changes
Merge pull request #99 from distantcam/master

Better use of Costura, allows for mono compatibility.
added option to specify files to copy as part of the Snow deployment
rebased from upstream