Convert to Swift 4.2#199

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benlachman wants to merge 9 commits intomatthewpalmer:masterfrom

nicemohawk:swift-4.2

Commits on Nov 6, 2018

Convert to Swift 4.2
benlachman
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Commits on Dec 17, 2018

Adds SWIFT_VERSION definition at 4.2
benlachman
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Removing target-level SWIFT_VERSION definitions. This should be done at the project level.
benlachman
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