[maven-release-plugin] prepare release Singularity-1.4.0

[maven-release-plugin] prepare release Singularity-1.3.0

[maven-release-plugin] prepare release Singularity-1.2.0

[maven-release-plugin] prepare release Singularity-1.1.0

[maven-release-plugin] prepare release Singularity-1.0.0

[maven-release-plugin] prepare release Singularity-0.23.0

[maven-release-plugin] prepare release Singularity-0.22.0

[maven-release-plugin] prepare release Singularity-0.21.0

[maven-release-plugin] prepare release Singularity-0.20.1

[maven-release-plugin] prepare release Singularity-0.20.0