Show more than just last logline on a puma error

[Mike Rogers]

Following on from #147 - which was a super helpful change, I think it would be really helpful to show more than just the last line. The reason is, quite often for me the last log line is:

unexpected exit:
	  /Users/Mike/.rbenv/versions/2.6.3/bin/puma:23:in `<top (required)>'

Which isn't that helpful, when a line higher up lines gives me a greater hint that I've forgot to bundle/run yarn.

Is it possible to capture the whole error on this page?