Fixed bug caused by the use of `%` on replacement string when calling
`string.gsub` (lua >= 5.2). According to
[lua-users](http://lua-users.org/wiki/LuaFiveTwo):
> ### string.gsub repl
>
> string.gsub
> [[6](http://www.lua.org/manual/5.2/manual.html#pdf-string.gsub)] now
> raises an error if the replacement string contains a '%' followed by
> a character other than the permitted '%' or digit.
In short, the replacement string does not require escaping of *magic
characters*.
