Changes version standard to use `-` character when available.
By convention `-` is translated to `.` from now on when the
`-` character is prohibited by downstream systems.
Closes: https://github.com/vmware/pyvmomi/issues/127
All development versions should be marked with yyyy.dev to denote that they are unstable development versions. Release versions will be marked 5.5.0_2014.1 (release 1) and so on with whole integer release numbers after the year.
This is the initial version of pyVmomi which represents vSphere API 5.1.
Going forward, expect only the 'Objects' and 'Types' generated source
files to need updating via official OSS drops.
