Revert "Intercept the error line number and calculate the actual line number using an offset."

This reverts commit e1d6a200d1cef23bdfcab2281041c858ff8b0e04.

I think intercepting the line number is not very reliable:

1. We might intercept the wrong string.
2. The error format might change in the future.
3. I have a better method to solve this problem. :laughing:
Solve the problem of having wrong line number in error message.

As mentioned in the previous commit, intercepting the line number
using regex is not realiable. I make use of the fact that the states,
ie, values of variables and all are preserved between .eval calls.

For example, this will print the value of `N`:

```javascript
jsrepl = new JSREPL();
jsrepl.loadLanguage('python');
jsrepl.eval("N = 10");
jsrepl.eval("print N");
```

Hence, we can separate the initialization and actual execution into
two .eval calls, ie, `.eval(input)` and `.eval(userCode)` and JSREPL
will report the correct line number in error message.