Tiny bug (fix) in entity_tmail.rb's from_tmail(tmail)

[LouisStAmour]

Seems there are instance variables in this method where there shouldn't be. Replace each so the method looks like this and you won't get any whiny nil errors about nil.header calls:

def from_tmail(tmail)
  raise ArgumentError, "Expecting a TMail::Mail object." unless tmail.is_a?(TMail::Mail)
  @headers ||= Hash.new {|h,k| tmail.header[k].to_s }
  if multipart?
    @content = tmail.parts.collect { |tpart| Entity.new.from_tmail(tpart) }
  else
    set_content tmail.body # TMail has already decoded it, but we need it still encoded
  end
end