Updated requirements

Mostly updated to latest versions, except:

• Flask
• SQLAlchemy

Both can't be updated with the current flask json api plugin (updated SQLAlechmy would require to update Flask-SQLAlchemy, which then would require to update Flask).

The latest Flask can't be used with the flask json api lib, as there are changes in the view classes that the flask json api lib is incompatible with.

(It tries to import classes that are no longer there).

I also removed the entry for urllib3. Due to the internal requirements of elasticsearch, requests & minio, it will install it anyway & pip will figure out the compatible version on its own.

Closes #128 (closed)