To check that the IsRunning method is working, some tests are needed. These tests shall be skipped when an AVdevice is not connected, such as when testing within Circle-CI.
av/device/device.go now contains the AVDevice interface and implementations of this
interface, namely, raspivid, geovision, webcam and file are contained in the packages
av/device/raspivid, av/device/geovision, av/device/webcam and av/device/file
respctively. config.go and testing was also moved to a new package called config.go in
order to remove would be circular dependency between AVDevice implementations and revid.
Modifications were made elsewhere expecting config.Config to be part of the revid package.
Scott