Change signature of MultipleFailureException.assertEmpty() to throw Exception.
Add back @Test tags accidentially removed in the previous commit
Fix typo in Javadoc
Indent with spaces (not tabs).
Don't create objects without a failure.
Use explicit auto-boxing.
Rewrite parts of the documentation.

Describe every expect method with a single test.
Revert changes of 128553f. Fixes #687.

Still fixes #121, but the original fix was superfluous. Added documentation
about handling assumes and asserts in conjunction with the
ExpectedException rule.
Fix documentation.
Extract isAnyExceptionExpected().

Improve readability and avoid duplicate code.