Add db:migrate to README

`bundle exec rake db:migrate`
Add .env to .gitignore
Link logo to dashboard when user signed in. Fixes #37
Merge pull request #38 from pdostal/patch-1

Add db:migrate to README
Merge pull request #39 from pdostal/patch-2

Add .env to .gitignore
Merge pull request #42 from johnthepink/update-logo-link

Link logo to dashboard when user signed in