Add env:example command

[svenluijten]

php artisan env:example should generate a file called .env.example (or overwrite if it already exists) with all the keys from the regular .env file. The example file should have empty values.

[patrikpihlstrom]

Mind if I give this a shot?

[svenluijten]

Actually, I'd rather clean up the codebase first before adding new features. Once I find some time I'll work on it.

[patrikpihlstrom]

Sounds good.