Heroku deployment

This would enable continuous deployment from our master branch.

Each time master is merged, travis deploys to heroku. There´re many upsides to automatic deployment from our master branch; instant feedback, better code-review before merge-ing and new features get pushed automatically right away when ready. 
One downside is the website downtime while deploying. This can be solved by buying a extra Dyno. Then we could enable heroku´s preboot feature which ensures no downtime at all and seamless deployments many times a day, just like netflix and flikr ;)