Remove redundant Docker tasks

Nothing and no one uses these.

docker/Dockerfile

@@ -1,39 +0,0 @@
-FROM python:3.6-slim
-
-ARG HTTP_PROXY
-ARG HTTPS_PROXY
-ARG NO_PROXY
-
-ENV PYTHONUNBUFFERED=1 \
-	DEBIAN_FRONTEND=noninteractive
-
-RUN \
-	echo "Install base packages" \
-	&& ([ -z "$HTTP_PROXY" ] || echo "Acquire::http::Proxy \"${HTTP_PROXY}\";" > /etc/apt/apt.conf.d/99HttpProxy) \
-	&& apt-get update \
-	&& apt-get install -y --no-install-recommends \
-		make \
-		curl \
-		git \
-		build-essential \
-		zip \
-		libpq-dev \
-	&& echo "Clean up" \
-	&& rm -rf /var/lib/apt/lists/* /tmp/*
-
-RUN \
-	echo "Install Cloud Foundry CLI" \
-	&& curl -sSL "https://cli.run.pivotal.io/stable?release=debian64&source=github" -o /tmp/cloudfoundry-cli.deb \
-	&& dpkg -i /tmp/cloudfoundry-cli.deb
-
-# these are declared statically here so that they're cached by the docker image - if we run after the `COPY` command
-# they won't be cached so it'll re-download every time. But these don't involve the filesystem
-COPY requirements.txt .
-COPY requirements_for_test.txt .
-RUN \
-	echo "Installing python dependencies" \
-	&& pip install -r requirements_for_test.txt
-
-WORKDIR /var/project
-
-COPY . .