Fix warnings in Swift 3.1

[onevcat]

No description provided.

[codecov-io]

Codecov Report

Merging #632 into master will increase coverage by 2.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #632      +/-   ##
==========================================
+ Coverage   75.81%   77.89%   +2.07%     
==========================================
  Files          21       21              
  Lines        2299     2352      +53     
==========================================
+ Hits         1743     1832      +89     
+ Misses        556      520      -36

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