Support Swift 4.1

[djones6]

Description

• Resolves a compilation error on Swift 4.1 on Linux due to changes to ObjCBool: ObjCBool: Add boolValue property apple/swift-corelibs-foundation#1223
• Adds Travis for Swift 4.1 (dev shapshot)

Motivation and Context

Demonstrate that Kitura will support the upcoming Swift 4.1 release.

How Has This Been Tested?

Travis with Swift 4.1 added to matrix

Checklist:

• If applicable, I have updated the documentation accordingly.
• If applicable, I have added tests to cover my changes.

[djones6]

Testcase failures that need resolving...

• TestCodableRouter.swift:696: error: TestCodableRouter.testCodableGetQueryParameters : XCTAssertTrue failed - Expected some bytes, received 0 bytes.
• TestCodableRouter.swift:743: error: TestCodableRouter.testCodableDeleteQueryParameters : XCTAssertEqual failed: ("badRequest") is not equal to ("OK") - HTTP Status code was badRequest

These fail on Linux and Mac, and only on Swift 4.1.

[djones6]

Should be resolved by Kitura/KituraContracts#14
I'll restart the CI

[codecov-io]

Codecov Report

Merging #1230 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1230   +/-   ##
=======================================
  Coverage   89.39%   89.39%           
=======================================
  Files          38       38           
  Lines        2234     2234           
=======================================
  Hits         1997     1997           
  Misses        237      237

Flag	Coverage Δ
#Kitura	89.39% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
Sources/Kitura/staticFileServer/FileServer.swift	92.51% <100%> (ø)	⬆️

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[ianpartridge]

Can we test against the latest snapshot please?

[djones6]

Updated to 03-04-a

[ianpartridge]

Travis update would be best.

[ianpartridge]

LGTM!