add methods expectXXXWith(assertionClass) to FluentExpectedException.

- add expectCauseWith(), expectRootCauseWith()
- rename assertWith to expectWith()
- split old AssertFactory on AssertFactory and ThrowableExtractor
- refactor tests, more DRY.
- add ProxiesFactory to remove all mess with AssertFactories
	and ThrowableExtractors from 'api' package and FluentExpectedException
	class.

Closes #9
pitest will be executed only in profile 'ci', travis integration.
unit test for FluentExpectedException.none().
javadoc enhancements.

Closes #2