Special characters aren't removed

[ankitbaphna]

https://github.com/codepath/interviewbit_solutions/blob/master/week_1/challenge_4.java#L4

Regex on line 4 should be : ("[^a-zA-Z]", " ") instead of ("^[a-zA-Z]", " ")

Please run on the given example and it won't give the expected answer with the provided solution.