Add mash installation

for_tests/Dockerfile

-from ubuntu:latest
+from ubuntu:18.04
 
 # Update apt-get packages
 RUN apt-get update &&\
@@ -14,6 +14,15 @@ RUN apt-get install -y \
 RUN pip3 install --upgrade pip
 
 
+# Install mash
+WORKDIR /tmp
+RUN wget https://github.com/marbl/Mash/releases/download/v2.2/mash-Linux64-v2.2.tar &&\
+    tar -xf mash-Linux64-v2.2.tar &&\
+    rm mash-Linux64-v2.2.tar &&\
+    mv /tmp/mash-Linux64-v2.2/mash /usr/local/bin &&\
+    rm -r mash-Linux64-v2.2
+
+
 # Install barrnap
 WORKDIR /tmp
 RUN wget https://github.com/tseemann/barrnap/archive/0.8.tar.gz &&\