Updating Docker files

Thanks @erasche for these changes from PR #204.

Dockerfile

@@ -1,26 +1,16 @@
-FROM ubuntu:16.04
-
-RUN apt update && \
-    apt install -y \
-        build-essential \
-        libffi-dev \
-        mysql-client \
-        python-dev \
-        python-pip && \
-    rm -rf /var/lib/apt/lists/*
-
-VOLUME ["/opt/CTFd"]
+FROM python:2.7-alpine
+RUN apk update && \
+    apk add python python-dev libffi-dev gcc make musl-dev py-pip mysql-client
 
 RUN mkdir -p /opt/CTFd
 COPY . /opt/CTFd
 WORKDIR /opt/CTFd
+VOLUME ["/opt/CTFd"]
 
 RUN pip install -r requirements.txt
-RUN pip install pymysql
 
 RUN chmod +x /opt/CTFd/docker-entrypoint.sh
 
 EXPOSE 8000
 
 ENTRYPOINT ["/opt/CTFd/docker-entrypoint.sh"]
-CMD ["gunicorn", "--bind", "0.0.0.0:8000", "-w", "4", "CTFd:create_app()", "--access-logfile", "/opt/CTFd/CTFd/logs/access.log", "--error-logfile", "/opt/CTFd/CTFd/logs/error.log"]

docker-compose.yml

@@ -11,8 +11,8 @@ services:
     volumes:
       - .data/CTFd/logs:/opt/CTFd/CTFd/logs
       - .data/CTFd/uploads:/opt/CTFd/CTFd/uploads
-    links:
-      - db:db
+    depends_on:
+      - db
 
   db:
     image: mysql