Specify Swift version without patch (fix #16)

[Jeehut]

This fixes #16. Basically it is a workaround for a weird Xcode 8.2 behavior which might not get fixed but instead defined as the new expected behavior, so we should update the framework.

[codecov-io]

Current coverage is 96.92% (diff: 100%)

Merging #17 into master will not change coverage

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  Hits            126        126          
  Misses            4          4          
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[Jeehut]

Note that in Xcode 8.2.1 this PR became obsolete as the weird behavior was fixed. You might still want to merge this though to cover Xcode 8.2.0.