Fix the Dockerfile's install link (#21)

* use compose profiles to make snekbox image optional.

* fix broken link

Author: AbstractUmbra

Dockerfile

@@ -37,7 +37,7 @@ RUN apt-get update \
     gnutls-dev \
     libmagic-dev
 
-RUN curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/install-poetry.py | python -
+RUN curl -sSL https://install.python-poetry.org | python -
 
 # copy project requirement files here to ensure they will be cached.
 WORKDIR /app