Use environment variables for tokens etc

...to facilitate Heroku deployment.
No need for .examples, migrating to Heroku

... so use environment variables now.
Update README and setup task to reflect new setup
Use consistent style for env vars
Convert carrierwave to use environment variables
Fix travis
Fix asset precompile issues
Change upload dir
Update md_preview to fix jquery related issues
Update jquery.scrollto and move to vendor assets
Create Procfile
Figaro for app configuration
Tweak figaro setup