tophat: add singularity files

src/singularity_modules/tophat/2.1.1/build.sh

+#/bin/sh
+sudo singularity build --force bin/tophat:2.1.1.sif src/singularity_modules/tophat/2.1.1/tophat.def
+singularity sign bin/tophat:2.1.1.sif

src/singularity_modules/tophat/2.1.1/tophat.def

+Bootstrap: docker
+From: ubuntu:18.04
+
+%labels
+MAINTAINER Laurent Modolo
+
+%post
+TOPHAT_VERSION=2.1.1
+PACKAGES=tophat=${BOWTIE2_VERSION}*
+
+apt-get update && \
+apt-get install -y --no-install-recommends ${PACKAGES} && \
+apt-get clean
+
+%environment
+export TOPHAT_VERSION=2.1.1
+
+%runscript
+exec /bin/bash "$@"