Add namespace Bk

bakara/src/bakara/core/string_fmt.h

@@ -5,8 +5,7 @@
 #include <exception>
 #include <algorithm>
 #include <cctype>
-
-// base case of recursion, no more arguments
+namespace Bk {
     void format_impl(std::stringstream& ss, const char* format) { 
         while (*format) {
             if (*format == '%' && *++format != '%') // %% == % (not a format directive)
@@ -53,3 +52,4 @@ std::string format(const char* fmt, Args... args) {
         format_impl(ss, fmt, args...);
         return ss.str();
     }
+}