Slather 2.4.0

• Xcode 8.3 support.
  ksuther
  #291

• Automatically ignore headers in Xcode platform SDKs.
  ksuther
  #286

• Automatically handle schemes with multiple build or test targets
  serges147
  #275

• Added TeamCity as a CI service option
  joshrlesch
  #279

• Handle UTF-8 characters correctly in HTML reports
  0xced
  #259

• Fix hanging xcodebuild invocation when getting derived data path.
  arthurtoper
  #238, #197, #212, #234