Issues running jit-diffs on windows

[AndyAyersMS]

Hit a couple of issues using this:

• Seems like JIT_DASM_ROOT must be set or app crashes.
• Windows requires .exe suffix for tools
• App should validate git is on path up front instead of crashing after running base set
• Framework DLL list seems outdated. Seems like you could just mine the test root.

[AndyAyersMS]

@russellhadley FYI...

I may work up some fixes.

[russellhadley]

@AndyAyersMS the frame work DLLs come via package so to update you only need to update the project.json, but the fx is only there to be used if CORE_ROOT isn't if you specify --core_root then that's where the framework dlls will come from.

[russellhadley]

Framework update issues tracked by #13. Closing remaining.