Numbers passed in first argument to bases.fromAlplabet cause a return value of 0

When you call

```javascript
bases.fromAlphabet(127, '0123456789abcdef'); 
```

returns `0`, but

```javascript
bases.fromAlphabet("127", '0123456789abcdef')
```

returns `295` (correct). 

The fix is to call `str = str.toString();` in the first line of `bases.fromAlplabet`.