Update DEPLOY.md

Fixed typo
Merge pull request #145 from LukeSwart/patch-1

Update DEPLOY.md
info about getting a dataset key
removed to-do note
Add a simple app.json file for deploying to heroku
Add shareabouts flavor and dataset config variables
Add a logo for the Heroku app
Remove migrate command from heroku postdeploy
Whitespace
Remove the postdeploy step
Ignore local environment files
Remove explicit scheme from assets so that map will work over https
Add a heroku deploy button to the readme
Refer to the configuration and deployment instructions from the Heroku deploy page
Use a shorter description (max 140 characters)
Disable failing tests
Merge pull request #147 from openplans/heroku-deploy

Heroku deploy button
greater focus on Heroku button for deploys
typo
link to info about Heroku button