--add: Make sed command compatible with BSD sed

Tested on sed from Mac OS X Mountain Lion, and with gsed from Homebrew.

Signed-off-by: Matt McClure <matthewlmcclure@gmail.com>
Merge branch 'avoid-sed-gnuisms'

Avoid using '\n' in the replacement of sed's substitute command.

* 'avoid-sed-gnuisms':
  --add: Make sed command compatible with BSD sed