remapping input characters

Was using maskedinput for restricted-alphabet keys and ran into a situation where we needed to re-map some erroneous entries (i.e., 'o' -> '0') instead of simply blocking the disallowed character. This pull implements a reMap setting. The above transform would be accomplished like:
```$("input.key").mask("xxxx-xxxx-xxxx",{placeholder:"x", reMap:{'o': '0'}});```

Presumptive, but thought it might be a feature worth sending up. Did my best to include a relevant test. 

Cheers