add cython, change FROM to alpine 3.10

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3-alpine
+FROM alpine:3.10
 
 COPY . /app
 WORKDIR /app
@@ -20,6 +20,7 @@ RUN \
         libressl \
         py3-lxml \
         py3-pip \
+        cython \
         python3 && \
     echo "**** install pip packages ****" && \
     pip3 install -U pip setuptools wheel && \

requirements.txt

@@ -1,3 +1,3 @@
 discord.py
 beautifulsoup4
-lxml
+git+https://github.com/lxml/lxml@master#egg=lxml