Add requirements file

[MarcoAGreco]

Add requirements to facilitate the dependencies installation.

[quirozity]

pip install pipenv
pip install flask
pip install flask_bootstrap
pip install flask_sqlalchemy
pip install flask_pymongo
pip install flask_login
pip install flask_wtf
pip install WTForms==2.3.3

requirements.txt

pip install -r requirements.txt

[berlotto]

@MarcoAGreco pipenv does it. Running pipenv install will install all dependencies.