Add regex matching to StringSubject (and omit from GWT).
Add a `doesNotContain()` method to StringSubject, add some tests, and fix null handling in StringSubject.
Add the Google copyright to these files.
Fix camel case on method name.
Merge pull request #81 from cgruber/stringregex

Add regex matching to StringSubject (and omit from GWT).
Merge pull request #82 from cgruber/notcontains

Add a `doesNotContain()` method to StringSubject