Powershell needs proper exit code
Default stability should not be final. Switched to alpha
Switched to default stability Beta because found ShortVersion assumed Beta. Short version uses now stability properly
Fixed review findings
Merge pull request #57 from danielmarbach/master

Powershell needs proper exit code
Introduced context class which has the Tip, CurrentBranch and Repo rather than setting properties down the line
No need to pass whole context object into Master Version finder
Tip is no longer set on context, it just delegates to Repository.Head.Tip