Swift 5 compatibility

[gereons]

Add Swift 5 compatibility. The podspec declares compatibility with both the 4.2 and the 5.0 compiler via the new swift_versions directive which is available as of cocoapods v1.7.0.

Fixes #207

[codecov]

Codecov Report

Merging #209 into develop will decrease coverage by 2.17%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #209      +/-   ##
===========================================
- Coverage    99.34%   97.17%   -2.18%     
===========================================
  Files            6        6              
  Lines          153      389     +236     
===========================================
+ Hits           152      378     +226     
- Misses           1       11      +10

Impacted Files	Coverage Δ
Sources/Generator.swift	100% <100%> (ø)	⬆️
Sources/Crypto.swift	100% <100%> (ø)	⬆️
Sources/Keychain.swift	92.56% <0%> (-4.81%)	⬇️
Sources/Token+URL.swift	98.41% <0%> (-1.59%)	⬇️

---

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[codecov]

Codecov Report

Merging #209 into develop will decrease coverage by 2.17%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #209      +/-   ##
===========================================
- Coverage    99.34%   97.17%   -2.18%     
===========================================
  Files            6        6              
  Lines          153      389     +236     
===========================================
+ Hits           152      378     +226     
- Misses           1       11      +10

Impacted Files	Coverage Δ
Sources/Generator.swift	100% <100%> (ø)	⬆️
Sources/Crypto.swift	100% <100%> (ø)	⬆️
Sources/Keychain.swift	92.56% <0%> (-4.81%)	⬇️
Sources/Token+URL.swift	98.41% <0%> (-1.59%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2414c60...790d4d0. Read the comment docs.

[mattrubin]

After wrestling extensively with Travis CI, I finally figured out how to get it to test both Swift 4.2 and Swift 5 with both xcodebuild and CocoaPods. This PR will be merged as part of #215. Thank you so much for your work on this!

[gereons]

You're welcome, and thanks for merging the PR. Do you plan to release this to the cocoapods mater repo soon?

[mattrubin]

@gereons OneTimePassword 3.2.0 has been pushed to the CocoaPods trunk! Please let me know if you have any issues upgrading.