Convering strings containing number

[Salih Dincer]

Hi,

I've been interested in conversion possibilities for a while.  I 
tried to convert a string containing numbers but with no success 
in single digits.  The only solution I found is to subtract 48 
from the result:

```d
import std;
void main()
{
     string str = "abc123";
     str[3..$].to!int.writeln; // 123
     auto bar = str[3].to!int;
     assert(bar == 49); // 49 is value for ASCII.
     writeln(bar - 48); // 1
}
```