Adds flask to the list of requirements.
It was missing for some reason.

add_hashtag is now wokring in flask_app.
It will later have to be changed though, as the current version is evrything but RESTful.

Next step is to display a list of currently tracked hashtag in the application.
Removes test file flask_stop from repo.
Adds method remove_hashtag to flask_app.

Next step is to generate a list of currently tracked hashtags in the main webpage
Structures the html templates a bit more and adds categories in the page.

NExt steps:
- List all currently tracked hashtags on main page
- Add icon to remove those hashtags next to them.