Info msg for missing config; strip email whitespace; mailinglist defaults

Random fixes for issues I ran into when configuring the notifier
with gitolite, but should be applicable most places.

- Allow for info message if the config.yml specified isn't found.
  It seems to be okay to not have a config file, but at least warn.
- I had whitespace between email addresses in the mailinglist
  config variable and the email didn't send to the second address.
  Stripping whitespace after splitting helps.
- Added a configuration variable to choose whether to prefer the
  git config hooks.mailinglist variable over the one in the
  config.yml. I'd like to use the git one if defined in my
  gitosis.conf but fallback to the one in the config otherwise.
Version bump to 0.11.9.1
and changelog
Merge pull request #176 from digitalcardboard/mistakes_i_made

Info msg for missing config; strip email whitespace; mailinglist defaults