Fix pod compilation in Xcode 10.2 about differencekit

[BjornRuud]

I had to get this working right away in my fork, and created a pull request in case the repo owner wants it.
#57

[gaetanzanella]

@BjornRuud +1

extension StagedChangeset: RandomAccessCollection, RangeReplaceableCollection, MutableCollection {
    public typealias Element = Changeset<Collection>

    // ...
}

did the trick in StagedChangeset.swift.

[ra1028]

@gaetanzanella
Xcode10.2 compatible version has been released.

[anlaital]

Should add spec.swift_version = '4.2' to DifferenceKit.podspec.

[BjornRuud]

Error with Swift 4.2 also. It seems the Swift 5 compiler doesn't like the Collection protocol conformance of StagedChangeset even in compatibility mode.

[MoElnaggar14]

I face the same problem

[Kaspik]

PR has been merged, I believe now @ra1028 just needs to do maybe some cosmetic changes in the project itself and then update version on CocoaPods etc.

[ra1028]

I'm now installing Xcode10.2 😂
One moment, please.