Remove sensitive data from repo history

I don't think you want your MongoHQ and AWS passwords public; that's a bad idea even if [you don't care who administers your content](http://voicesfromghana.com/admin/dashboard).

Assuming you want to keep this on GitHub, the easiest way to fix the problem is probably to change your MongoHQ password and revoke the AWS access key you've made public, as they're baked into the repository history now. But in case you don't want to do that for some reason, I've purged the offending file (`.env`) from the repository history in this pull request.

Note that simply merging the pull request does not help, as the current history (including `.env`) would be preserved by the merge. Instead, you need to drop the current master branch and use the `no-secrets` branch from this pull request instead.

Also, hi. I'm `rscr` on [subrosa](https://subrosa.io/app) now if you want to talk.