htseq: add singularity files

src/singularity_modules/htseq/0.8.0/build.sh

+#/bin/sh
+sudo singularity build --force bin/htseq:0.8.0.sif src/singularity_modules/htseq/0.8.0/htseq.def
+singularity sign bin/htseq:0.8.0.sif

src/singularity_modules/htseq/0.8.0/htseq.def

+Bootstrap: docker
+From: ubuntu:18.04
+
+%labels
+MAINTAINER Laurent Modolo
+
+%post
+HTSEQ_VERSION=0.8.0
+PACKAGES="build-essential \
+python3-pip \
+python3-setuptools \
+python3-dev \
+python3-wheel"
+
+apt-get update && \
+apt-get install -y --no-install-recommends ${PACKAGES} && \
+apt-get clean
+
+pip3 install numpy==1.14.3
+pip3 install pysam==0.15.0
+pip3 install HTSeq==${HTSEQ_VERSION}
+
+%environment
+export HTSEQ_VERSION=0.8.0
+
+%runscript
+exec /bin/bash "$@"