Example WGS VG workflow not compatible with wdl version 1.0

[cmarkello]

Example wdl VG pipeline in https://github.com/vgteam/vg_wdl/blob/master/workflows/vg_pipeline.workingexample_tiny.wdl
is not syntactically compatible with wdl version 1.0 and is instead compatible with a development version.

I'll need to find the exact version of wdl that that workflow works in and explicitly define it in the workflow.

[cmarkello]

Current version of cromwell (36.1) as of the time of this note doesn't parse the version line in wdl files if the wdl version is a draft version.
The Cromwell 36.1 wdl parser defaults to draft-2 if a version line in the wdl file is not present.