update timber-comment.php to have avatars

Ok, take 2. This is working well for me.  Tested it with the various default settings and email addresses with & without gravatars. There are no tests though. not 100% sure how i would do that but willing to have a go. Do you have a test suite for this?

Let me know if i need to tidy it up / its generally no good / any other feedback.
Merge branch 'patch-2' of github.com:asecondwill/timber into asecondwill-patch-2

* 'patch-2' of github.com:asecondwill/timber:
  update timber-comment.php to have avatars
Updating to handle authors on anonymous comments
removed avatar stuff for now so i can merge user updates
Merge branch 'asecondwill-patch-2' into dev

* asecondwill-patch-2:
  removed avatar stuff for now so i can merge user updates
  Updating to handle authors on anonymous comments
  update timber-comment.php to have avatars