save converted actual result as reference

[johnnychen94]

For images as txt, we should save the converted string contents: savefile(file, actual) instead of images savefile(file, raw_actual).

Another bug I introduced in #37 😂

No test for this because interactive REPL is required.

[coveralls]

Coverage increased (+0.6%) to 83.721% when pulling a347c6e on jc/new_ref into 9a5ae50 on master.

[johnnychen94]

I forgot to do a rebase on latest master branch before pushing this. Since the PR test has passed I'll just merge it without waiting for another round of tests.