Mongoose: solving more of depreciation warnings

fixes for redirect from /discussions route to particular discussion

set content to empty string after creation of new Discussion

README (Stripe), proper name for S3 bucket

merge experiment into master

removed public/private Discussion, instead TL chooses members

MobX for pages: YourProfile, TeamProfile, TeamMembers

login redirects for invited, existing, new user.

copy URL to clipboard for Discussion; removed TeamConstraints page

MIT licence, added config for deployment to Zeit Now