Cleanup

As PHP-VCR gets used more, there is a need for a very stable code which can be easily extended in the future. To ensure good code quality this cleanup will:

 - [ ] Add PHP docblocks
 - [ ] Code coverage > 90%
 - [ ] Move Filters into own namespace
 - [ ] Move Client, SoapClient and Assertion into Util namespace
 - [ ] Try to not hit the network in unit tests