Test for threading issue with time zone cache
Test case for #31.
Apparently `TEST_AFTER_BUILD` doesn’t work anymore. Yay!
Added a destination specifier for iOS, so that xcodebuild doesn’t assume I want to run on a device that isn’t present.
Wrap the time-zone cache in an object that stores it in the thread dictionary. Should improve thread safety and thereby fix #12. (However, I have not tested it in a multi-threaded situation.)
Merge branch 'master' of https://github.com/boredzo/iso-8601-date-formatter