Update to latest nan package that contains a fix for Windows build error: node_modules\nan\nan_maybe_43_inl.h(112): error C2039: 'ForceSet': is not a member of 'v8::Object' (compiling source file ..\src\ed25519.cc) [C:\PassportSqrl\node_modules\ed25519\build\ed25519.vcxproj]
Fix gyp path to OpenSSL on Windows to handle layout changes in 1.1.0+
Add prereq info in README to make it easier to get started