Any plans to support swift 4.x?

[Nonnus]

New Issue Checklist

• I have tried with the latest version of OHHTTPStubs
• I have read the README
• I have read the Using the right Swift Version of OHHTTPStubs for your project section
• I have searched in the existing issues
• I have read the OHHTTPStubs wiki to see if there wasn't a detailed page talking about my issue

Environment

• version of OHHTTPStubs: [LIB VERSION HERE]
• integration method you are using:
  • Cocoapods
  • Carthage
  • submodule
  • other
• version of the tool you use: [INSERT VERSION HERE]

Issue Description

Whenever i try to rebuild OHHTTPStubs with XCode 9.x / Swift 4.x using carthage i get a warning stating framework was build with swift 3.1

Complete output when you encounter the issue (if any)

*** Skipped installing OHHTTPStubs.framework binary due to the error:
	"Incompatible Swift version - framework was built with 3.1 (swiftlang-802.0.53 clang-802.0.42) and the local version is 4.1 (swiftlang-902.0.48 clang-902.0.37.1)."

[Olivier Halligon]

See #277