Check format of release number
Check format of release number

Abort with usage if bad.
Fixes #10.

jouvin/release,quattor/release,stdweird/release,jrha/release,quattor/release,quattor/release,jrha/release,brunocanning/release,brunocanning/release,wdpypere/release,jouvin/release,wdpypere/release,jouvin/release,stdweird/release,brunocanning/release,wdpypere/release,jrha/release