Add singularity recipe script for 0.3.3

singularity/Singularity.0.3.3

+Bootstrap: docker
+From: bilbydev/test-suite-py3
+
+%help
+A singularity container for running bilby scripts
+
+%post
+export PATH=/opt/conda/bin:${PATH}
+echo "Installing latest bilby version"
+pip install bilby==0.3.3
+
+%environment
+echo "Add Multinest library environment variable"
+LD_LIBRARY_PATH=/MultiNest/lib
+export LD_LIBRARY_PATH