Update requirements.txt

update python version in runtime.txt and Dockerfile, fix sqlalchemy 1…

….4.x bug

Update runtime.txt

FLASK_APP not set correctly fix

bug fixes, upgrade deps, security fixes (#75)

* Update README.md

* Update CONTRIBUTING.md

* fixes and more strict security headers

Update README.md (#74)

* Update README.md & CONTRIBUTING.md

Update README.md

docker-compose fixes | redirection bug fixed | admin views modified

Merge pull request #60 from abs0lut3pwn4g3/gssoc20-dev

**Release v1.0**

New features:
- [x] Multiple boxes support (closes issue #17)
- [x] Challenges page (closes issue #56). Along with tag and category models for organization.
- [x] CTF settings and websites are now stored in database and can easily be changed from the new `/setup` view. (Closes issue #55)
- [x] WTForm class for Machine for editing/creating new machines.
- [x] Implemented thorough and efficient caching with use of "Flask-Caching" and "Redis".
- [x] Now uses flask factory app method so the various flask extensions can be well-managed.

Changes:
- [x] Define redis service in `docker-compose.yml`
- [x] Redis add-on has been added to `app.json`.
- [x] `ADMIN_EMAIL`, and mail related env variables added in `app.json`.
- [x] Flag submission is now in a modal.
- [x] DB models are now in their respective folders in `models.py`
- [x] Optimized scoreboard's detail fetching
- [x] Features such as searching and exporting and new dark theme for `Admin Controls` (closes issues #1, #16, #36 )
- [x] Some utility functions such as `@admin_only` decorator.
- [x] macros have been defined in templates for reusability.

Update README.md