Unable to build on Heroku

[loganwright]

I'm getting several errors related to threading when building on Heroku which is Ubuntu 14.1 I believe:

remote: /tmp/build_aededebadd4c4d1e6daca762e1f8b226/Packages/MongoKitten-0.2.1/Sources/Server.swift:45:35: error: use of unresolved identifier 'dispatch_get_global_queue'
remote:     private let backgroundQueue = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
remote:                                   ^~~~~~~~~~~~~~~~~~~~~~~~~
remote: /tmp/build_aededebadd4c4d1e6daca762e1f8b226/Packages/MongoKitten-0.2.1/Sources/Server.swift:45:61: error: use of unresolved identifier 'QOS_CLASS_BACKGROUND'
remote:     private let backgroundQueue = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
remote:                                                             ^~~~~~~~~~~~~~~~~~~~
remote: /tmp/build_aededebadd4c4d1e6daca762e1f8b226/Packages/MongoKitten-0.2.1/Sources/Server.swift:81:9: error: use of unresolved identifier 'dispatch_async'
remote:         dispatch_async(backgroundQueue, backgroundLoop)
remote:         ^~~~~~~~~~~~~~
remote: /tmp/build_aededebadd4c4d1e6daca762e1f8b226/Packages/MongoKitten-0.2.1/Sources/Server.swift:104:9: error: use of unresolved identifier 'dispatch_async'
remote:         dispatch_async(backgroundQueue, backgroundLoop)
remote:         ^~~~~~~~~~~~~~

Really looking forward to this library, let me know if I can help resolve this issue.

Using: Development Snapshot 2016-03-01-a