Fix bug with stripping spaces on last line in WordUtils.wrap()

In _WordUtils.wpap()_ leading white spaces on new lines are stripped from the result. But there is a bug if there are multiple white spaces on the last line. For example:
```java
input = "word1             word2                        word3";
System.out.println(WordUtils.wrap(input, 7));
```
The result will
```
word1  
word2  
  word3
```
Expected result is
```
word1  
word2  
word3
```

I propose fix contained in this pull request.