Add Build for PSCore/Linux/OSX #30
Description
PSCore GA is aimed for Mid-Jan, and there's quite a few bugs with 5.1 that won't be fixed (i.e. Publish-Module), so would be good to start including those in the build tasks...
PowerShellGet as a nice example of those: https://github.com/PowerShell/PowerShellGet/blob/development/.travis.yml