Errors and warnings when building with Visual Studio 2015

[AntAgna]

I experienced a few errors and warnings when compiling master with Visual Studio 2015.

• Name collision with free and new macros when using memory leak detection
• Two minor warnings in format.cpp
• Type conversion warning (int to wchar_t) in format.cpp
• bad_conversion class uses non public inheritance of std::exception caused warnings C4673 and C4670

The last one is a significant bug since it means exceptions would not have been caught by catch (const std::exception& e).

[billyquith]

Name collision with free and new macros when using memory leak detection

Hopefully you didn't find any leaks. I haven't tested for them myself.

[billyquith]

Type conversion warning (int to wchar_t) in format.cpp

Thanks for your work here but I think I may just remove fmt and use iostream. See #59. Just one less dependency.

[AntAgna]

I have seen no leaks