StopAtEOF: keep sending lines until EOF

[Luap99]

When a StopAtEOF() is called the code should continue to send all lines to the Lines channel. The issue here is if the caller is not ready to receive a new line the code blocks as it is using a unbuffered channel. However <-tail.Dying() would return in this case so the line was skipped. This means that the caller did not get all lines until EOF. Now we still want to skip in case any other reason for kill was given therefore add special logic to only not read the Dying channel on the EOF case.

The one downside is that StopAtEOF() could block forever if the caller never reads new Lines but this seems logical to me. If the caller wants to wait for EOF but never reads remaining Lines this would be a bug on their end.

Fixes #37