Updated to latest Roslyn

[filipw]

Latest on the nightly feed is v1.1.0-beta1-20150629-03 right now

[filipw]

Currently the engines here run 1.0.0-rc2

[filipw]

I have the upgrade ready on this branch https://github.com/scriptcs/scriptcs-engines/tree/feature/roslyn-upgrade

However, it requires VS2015 in order to build due to the dependencies of the Roslyn 1.1.0-beta1 packages