Update plugins (akismet / cloudflare / contact-form-7)

Hello,
While setting up our WordPress site, I found that there're several plugins outdated and thus made this pull request.
All of them are patch level updates, so they might not introduce any significant changes but just bug fixes.

* akismet 2.5.6 -> 2.5.9
* cloudflare 1.3.9 -> 1.3.10
* contact-form-7 3.5.2 -> 3.5.3

Thanks for your nice work brining WordPress to Heroku! :+1: