Made package compatible with go modules, added hcl2 compatible

Author: Edwin Hermans

go.mod

@@ -0,0 +1,11 @@
+module github.com/lmars/packer-post-processor-vagrant-s3
+
+go 1.13
+
+require (
+	github.com/aws/aws-sdk-go v1.29.23
+	github.com/blang/semver v3.5.1+incompatible
+	github.com/hashicorp/hcl/v2 v2.3.0
+	github.com/hashicorp/packer v1.5.4
+	github.com/zclconf/go-cty v1.3.1
+)