Update LuaContext.hpp to not include misc/exception.hpp in Visual Studio 14.0 (2015)

[eliaskosunen]

Currently, LuaContext.hpp always includes the header file "misc/exception.hpp" if the compiler is MSVC++. This causes compilation errors in VS 14.0, since these functions are already defined in the standard library. Hence, a check against the version number is required.

[DouglasHeriot]

I have also fixed this in #2

[Habbie]

This says 1800, #2 says 1900, can either of you comment on which is correct?

[eliaskosunen]

1800 means VS 2013 and 1900 means VS 2015. This PR says _MSC_VER <= 1800 which refers to VS 2013 initial release and before, #2 says _MSC_VER < 1900 which would refer to every version before VS 2015.

I'd say #2 is more correct, since it includes every minor release of VS 2013 as well.

[eliaskosunen]

I changed this PR to contain a similar check to #2.

[Habbie]

Thanks!