Trailing newline on raw responses

Without this you cannot easily share patches:

    user@machine1 $ git diff | curl -F 'content=<-' https://dpaste.de/api/
    user@machine2 $ curl https://dpaste.de/xxxx/raw/ | git apply
    fatal: corrupt patch at line 67
Allow raw snippets without trailing slash

Fixes an asymmetry where both of

  curl https://dpaste.de/xXxx
  curl https://dpaste.de/xXxx/

work, but

  curl https://dpaste.de/xXxx/raw/

fails without a trailing slash (because curl doesn't follow redirects by
default).
Merge pull request #22 from mgedmin/better-raw-responses

Better raw responses