hisat2: add samtools to docker

src/docker_modules/hisat2/2.0.0/Dockerfile

-FROM ubuntu:18.04
+FROM samtools:1.7
 MAINTAINER Nicolas Fontrodona
 
 ENV HISAT2_VERSION=2.0.0
-ENV PACKAGES unzip=6.0* \
-   gcc=4:7.3.0* \
-   g++=4:7.3.0* \
-   make=4.1* \
-   python \
-   curl=7.58.0* \
-   ca-certificates=20180409 
+ENV PACKAGES curl \
+             zip \
+             g++ \
+             perl \
+             python
 
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends ${PACKAGES} && \
-    apt-get clean
+RUN apk update && \
+    apk add ${PACKAGES}
 
 RUN curl -k -L http://ccb.jhu.edu/software/hisat2/downloads/hisat2-${HISAT2_VERSION}-beta-source.zip -o hisat2_linux-v${HISAT2_VERSION}.zip && \
 unzip hisat2_linux-v${HISAT2_VERSION}.zip && \
@@ -20,5 +17,4 @@ cd hisat2-${HISAT2_VERSION}-beta && \
 make && \
 cp hisat2 /usr/bin && \
 cp hisat2-* /usr/bin && \
-rm -Rf hisat2-${HISAT2_VERSION}-beta 
-
+rm -Rf hisat2-${HISAT2_VERSION}-beta