Fix helios console command to work with Foreman ~> 0.63

Starting from 0.63, foreman has switched to Dotenv instead of
foreman-env.

This patch upgrades the foreman dependency to ~> 0.63, and fixes the
`helios console` command by merging the @env hash with values from
Dotenv::Environment.
Merge pull request #38 from bartvandendriessche/fix_console_for_foreman_0.63

Fix helios console command to work with Foreman ~> 0.63
Removing Gemfil.lock from example
Compacting Rack::Cascade to avoid call to nil

Flattening namespace of Helios::Application