Update for MSVC 14 CTP2

- update the last tested version to suppress the "unknown compiler version" warning spam
- fix a comment still mentioning version 18 instead of 19
- with CTP2, MSVC 14 is now officially 2014, which is now reflected in the comment as with the other versions
Merge pull request #30 from MarcelRaad/patch-2

Update for MSVC 14 CTP2