Xcode 9 swift 4

[ghost]

Resolves #64 Update to Xcode 9.1 and Swift 4.0.

• Migrate to Swift 4
• Update dependencies
• Update CI to Xcode 9.1
• Update SwiftLint to 0.24.0
• Update .swift-version to 4.0
• Ensure correct version of Ruby when running on Travis CI

[codecov-io]

Codecov Report

Merging #65 into v3_0 will not change coverage.
The diff coverage is 91.66%.

@@           Coverage Diff           @@
##             v3_0      #65   +/-   ##
=======================================
  Coverage   59.67%   59.67%           
=======================================
  Files          44       44           
  Lines         548      548           
=======================================
  Hits          327      327           
  Misses        221      221

Impacted Files	Coverage Δ
...urces/Configurations/CreditCardConfiguration.swift	96.66% <ø> (ø)	⬆️
Sources/Controls/ValidatorTextField-UIKit.swift	20.53% <0%> (ø)	⬆️
Sources/Conditions/AlphanumericCondition.swift	100% <100%> (ø)	⬆️
Sources/Conditions/RangeCondition.swift	100% <100%> (ø)	⬆️
Sources/Conditions/CreditCardCondition.swift	86.66% <100%> (ø)	⬆️
Sources/Conditions/NumericCondition.swift	100% <100%> (ø)	⬆️
Sources/Conditions/PasswordStrengthCondition.swift	90.47% <100%> (ø)	⬆️
Sources/Validators/CreditCardValidator.swift	100% <100%> (ø)	⬆️
Sources/Conditions/AlphabeticCondition.swift	100% <100%> (ø)	⬆️
Sources/Protocols/Condition.swift	100% <100%> (ø)	⬆️

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