Update swift keywords and attributes for Swift 2
Update swift keywords and attributes for Swift 2

This updates the swift.vim syntax file with new keywords and attributes
that were introduced in Swift 2.0

Additional information about these new keyword and attributes may be
found in "The Swift Programming Language" (Swift 2 Prerelease) [1]

[1]: https://itunes.apple.com/us/book/id1002622538

aclissold/swift.vim,ajh17/swift.vim,panghea/swift.vim,mokagio/swift.vim,michaelnisi/swift.vim,gfontenot/swift.vim,keith/swift.vim