Add .env to gitignore.
Add .env to gitignore.

Running with foreman (heroku) allows you to use .env files to set
environment variables and this file should not be committed to the repo.

mongodb-labs/mongo-web-shell,xl76/mongo-web-shell,10gen-labs/mongo-web-shell,pilliq/mongo-web-shell,pilliq/mongo-web-shell,FuegoFro/mongo-web-shell,xl76/mongo-web-shell,rcchan/mongo-web-shell,pilliq/mongo-web-shell,mcomella/mongo-web-shell,mongodb-labs/mongo-web-shell,10gen-labs/mongo-web-shell,lnickers2004/mongo-web-shell,lnickers2004/mongo-web-shell,mcomella/mongo-web-shell,10gen-labs/mongo-web-shell,mcomella/mongo-web-shell,FuegoFro/mongo-web-shell,FuegoFro/mongo-web-shell,mongodb-labs/mongo-web-shell,rcchan/mongo-web-shell,ecbtln/mongo-web-shell,ecbtln/mongo-web-shell,lnickers2004/mongo-web-shell,lnickers2004/mongo-web-shell,ecbtln/mongo-web-shell,rcchan/mongo-web-shell