swift-package-manager comatibility

[ahti]

Since Turnstone is currently not compatible with the Swift Package Manager, it can't currently be integrated with Curassow on platforms where CocoaPods is not available (Linux).

As far as I see nothing but the Podfile and the name of the source files directory would need to change, but I am just getting started with the whole Swift package management thing.

[kylef]

@Ahti This library won't work on Linux until Foundation on Linux get's regex support, so Linux support is blocked until that happens first.

[sauliusgrigaitis]

@kylef looks like there is progress on NSRegularExpression.