Use 'i' as an alias for a decimal specifier

Was unable to use sprintf.js as a drop-in replacement, the specifier `i` was not recognized.

It's an old convention, `%i` is seen in both [C sprintf](http://www.tutorialspoint.com/c_standard_library/c_function_sprintf.htm) and [C++ sprintf](http://www.cplusplus.com/reference/cstdio/printf/).