{string}.replace(..) add support for providing name-value pairs

In addition to supporting the current

``` coffee
result = "stringA".replace('a','b')
```

also add support for

``` coffee
stringA.replace({ 'a':'b' , 'c' : 'd' })
```

which would be equivalent to 

``` coffee
stringA.replace('a','b').replace('c','d')
```
