boon/src/main/java/org/boon/Str.java
@Universal
    public static String atIndex( String str, int index, char c ) {
            return idx (str, index, c);
    }
@Universal
    public static String atIndex( String str, int index, char c ) {
            return idx (str, index, c);
    }
Puts character at index
@param str string
@param index index
@param c char to put in
@return new string