github_issue_converter.py also imports comments which are marked as deleted

```
What steps will reproduce the problem?

Have an issue with deleted comments, like 
https://code.google.com/p/tortoisegit/issues/detail?id=48, comment #16 is 
deleted

What is the expected output? What do you see instead?

This comment must not be migrated. - It is migrated.
```

Original issue reported on code.google.com by `sstrickr...@googlemail.com` on 11 Apr 2015 at 4:46
