Update author.rb

This pull request will make rgit more server-like and will give it networking functionality

`m[4]` is regexp matched string so there is no need it 'to_s' method.
Furthermore, author_string does not contain any ip addresses.
This string originates from author/committer lines of `git log --format=raw` command and looks like this:

`Scott Chacon <schacon@gmail.com> 1252081154 -0700`

So, what's the point of your changes?