Unittests update

Added _skips_ for tests that require _Phalcon_ or _Fabfuel/Mongo_ extension and moved those two to suggested list in composer.
Most tests base on Interfaces than concrete implementations,  also simplified them in few cases.
Also added usleep() - test were failing when ran on faster machines or without coverage.

Yup, but this should be tested in separate test, and not only as `assertInstanceOf` but also `assertSame` and not for example the first one.