Merge pull request #6 from PrivacySolutions/master

Merge pull request from orignal/master
fix vs2013 build, constexpr require VC++ November 2013 CTP update

Visual C++ Compiler November 2013 CTP
http://www.microsoft.com/en-us/download/details.aspx?id=41151
Merge pull request #92 from chertov/master

fix vs2013 build, constexpr require VC++ November 2013 CTP update