Import code from gem v2.6.6
Don't log Erubis::VERSION on each invocation
patch erubis-rails to only escape html templates [bugid:693]

see Fjan's comment:
https://rails.lighthouseapp.com/projects/8994/tickets/4858-actionmailer-is-html-escaping-ampersand-in-urls-in-plain-text-messages#ticket-4858-25
Rails 3 has a slightly different patch (see link)
fix (re-enable) auto html escaping [bugid:1207]

oops. a tweak of mine to prevent html escaping in plaintext emails (and any other non-html page renders) went awry and disabled auto-escaping entirely.
my mistake: "format"s that come through are "text.plain" and "html", but not "text.html".
fix erubis spec

- add correct version
- return spec