Added Set struct + tests
merge master from upstream
Merge branch 'master' of https://github.com/maxpow4h/swiftz
Added minus,intersect and Printable + tests
Added more set operations + overloaded operators.
Merge branch 'master' of git://github.com/tLewisII/swiftz

Conflicts:
	swiftz.xcodeproj/project.pbxproj
Added any? and Set() to Set