Fix copyright headers missed in previous sweep

Turns out that `ag` ignores the files in the spec/acceptance directory
due to a bug in its handling of `.gitignore` files. The upstream issue
is:

https://github.com/ggreer/the_silver_searcher/issues/168
Simplify remaining spec_helper requires

For the same reason as the previous commit, `ag` didn't catch these
files in its sweep.