fixed bug occurring when a line contains both a valid directive and a comment

I found a bug when you have a line containing both a directive and a comment, like:
```
Disallow: /      #comment
```
My edit strips away the comment, in each line, before the explosion of the string on the double colon. In this way the explode(':', $line) is executed on this string:
```
Disallow: /      
```