Fix output of NaN on msvc-14.

See: http://blogs.msdn.com/b/vcblog/archive/2014/06/18/crt-features-fixes-and-breaking-changes-in-visual-studio-14-ctp1.aspx
Merge pull request #11 from mkurdej/fix/nan-output-msvc-14

Fix output of NaN on msvc-14.
Thanks!