Replace `#=>` with `# =>` [ci skip]

@rafaelfranca, I realized I made a couple of commits to docrails with the same syntax `#=>` that you corrected in f7c7bcd9 with `# =>`. :sob:

If you'd like, I can push this new commit to docrails to fix *all* the occurrences of `#=>` in the code documentation once and for all.

I know this is cosmetic change.. but it's also just in the documentation.
Should I ship it or not?

[ Note… this specific Pull Request is against my own fork of docrails because docrails says DO NOT OPEN PULL REQUESTS. If you think this commit should go, I'll push it to rails/docrails ]