Temporarily disabled VC warning C4702.

The warning is for unreachable code (around [line 166 of clara.h](https://github.com/philsquared/Catch/blob/master/include/internal/clara.h#L166) shown below):

    virtual void setFlag( C& obj ) const {
        typename RemoveConstRef<T>::type value;
        convertInto( true, value );  // This throws if value is of type std::string
        function( obj, value );  // warning C4702
    }

This ultimately comes from `bindProcessName`, where `convertInto` has args of type `bool` and `std::string`.