Issue #6 Add a separate last releases table so that RequestCounts
records do not need to be kept for much longer treshold
'allowReleasedUserOnAddressFor' . 
- RequestCountsRepository renamed to DbalGateway
- TresholdsGovernor renamed property requestCountsRepo to
requestCountsGateway
- TresholdsGovernor 
	::constructor DbalGateway (2 properties: requestCoutnsGateway,
releasesGateway
	::initFor releasesGateway aanroepen aanpassen
	::releaseUserNameForIpAddressAndCookie now also inserts or updates
releases
- DbalGateway isUserReleased functions now query the releases table
	::insertOrUpdateRelease, ::deleteReleasesUntil added
- TresholdsGovernorTest testDelete functions now also delete releases
 
Issue #9 cross framework library refactoring
- doc/Installation.md added instructions for use without Symfony 2