make app deployment easier

- adds new rake task app:deploy 
  which in turn calls `db:migrate`, `council_districts:load`,
  and `legistar_all:refresh`.
- uses task in app.json for auto deploy and in README
add website to app.json

- Note that currently the website and repo url are 
  the same but that may change eventually (if we create a github pages 
  landing page for instance).
Merge branch 'feature/deploy-to-heroku-button' of github.com:codeforamerica/MuniciPal into feature/deploy-to-heroku-button
remove trailing whitespace