Merge pull request #25 from DedMaroz/master

treating fixtures as resources + dropping unused constructor from WebDriverReleaseManager
Re-implimenting a session tracker after a pull/merge went horribly horribly wrong
Bringing back grid_status end point, since all the nodes will now run in a single mode
Adding concept of tracking sessions before reboot
fising grid status endpoint test
Adding logic to reboot node after X many test runs