v0.3.1

Minor patches and updates

What's Changed

• update testing data files with new grid structure by @gauravharsha in #32
• remove Green's function update from "diff" function in Dyson. by @gauravharsha in #37
• add grids version string to WINTER output by @gauravharsha in #38
• check if results_file exists before running winter job. by @gauravharsha in #39

Full Changelog: v0.3.0...v0.3.1