Update README

README.md

 # marketo-tools
 
 This is a simple Sinatra application that receives GitLab.com sign-up hooks and
-passes the relevant information into a Marketo email list.
+passes the relevant information to Marketo leads.
 
 This replaces our internal [mailchimp-tools] project.
 
@@ -13,11 +13,22 @@ This replaces our internal [mailchimp-tools] project.
 
 ## Development
 
+```sh
+bundle install
+bundle exec rackup -p 4567
+open http://localhost:4567/
+```
+
 ## Deployment
 
+This project stores HTTP Basic Auth credentials and Marketo API keys in the
+environment, using [Dotenv]. The default values should be overridden in a
+`.env.production` file.
+
 ## License
 
 Copyright © 2015 GitLab, Inc. It is free software, and may be redistributed
 under terms specified in the [`LICENSE`](LICENSE) file.
 
 [mailchimp-tools]: https://dev.gitlab.org/gitlab/mailchimp-tools
+[Dotenv]: https://github.com/bkeepers/dotenv