create single-click Heroku hosting and documenation (#834)

* add deploy button

* Fix info

* Create heroku.yml

* Remove unnecessary files

* add buildpack

* Add container stack

* Remove comment

* Remove comment

* fix stack name?

* Move run to heroku.yml with port var

* Add dataset env var

* Add dataset env var

* Revert "Remove unnecessary files"

This reverts commit b2cb34dccb.

* move Dockerfile

* create readme

* add back preexisting Dockerfile

* remove button

* Add quick start and caveats

* add what and why section

* remove README

* add deploy button

* Fix info

* Create heroku.yml

* add buildpack

* Add container stack

* Remove comment

* Remove comment

* fix stack name?

* Move run to heroku.yml with port var

* Add dataset env var

* Add dataset env var

* move Dockerfile

* create readme

* add back preexisting Dockerfile

* remove button

* Add quick start and caveats

* add what and why section

* remove README

* wording fix

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* fix link

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* replace github links with S3 buckets

* small fixes

* grammar and spelling changes

* add hibernation caveat

* more spelling

* revise what is heroku

* rewording

* rename header

* revise caveats

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* various changes

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Charlotte Weaver <charlottesweaver@gmail.com>

* Update experiments/heroku/README.md

Co-Authored-By: Sidney Bell <sidneymbell@users.noreply.github.com>

* Update experiments/heroku/README.md

Co-Authored-By: Sidney Bell <sidneymbell@users.noreply.github.com>

* revisions/additions

heroku.yml

@@ -0,0 +1,5 @@
+build:
+  docker:
+    web: experiments/heroku/Dockerfile
+run:
+  web: curl -o dataset.h5ad $DATASET && cellxgene launch dataset.h5ad --host 0.0.0.0 --port $PORT