Added QUnit tests.

I've added some basic unit tests:
- no-locale.html tests when the correct behaviour of strings when no locale has been set.
- one-locale.html tests, when one locale has been set, the behaviour when a locale is specified and not.
- two-locale.html tests with two locales (English and Chinese) the conditions when a locale is not specified, when one locale is specified, and when one locale is specified with a default locale.