Ensure Erubis is available.

It should be part of the bundle in case it's not on the system.
Print out the path of the file being written.

Maybe more useful than the Object id?

There's some commit noise due to whitespace changes here - sorry. If it's
any consolation, it's the removal of trailing whitespaces...
Allow linking to specific lines.

This is slightly hacky, but seems like a useful thing to be able to do
for any online version of a play - be able to link to "Tomorrow, and
tomorrow, and tomorrow, creeps in this petty pace" and so on.

I've replaced the `<br/>` tags with spans, so that the line links can
be shown only when hovering over a line. I don't think this should
break anything and it still looks good in my browser at least.
Merged in and regenerated