Upgrade to Insta master to get bugfix.

Map sorting in Insta was previously not recursive.
As of this PR, it is!
https://github.com/mitsuhiko/insta/pull/80

Since it hasn't made it into a release yet, but is
important for Rojo to have snapshot determinism,
we're moving temporarily to depend on Insta via Git.

rojo-test/serve-test-snapshots/serve_test__just_txt_all.snap

@@ -4,16 +4,16 @@ expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:
   id-2:
-    Id: id-2
-    Parent: ~
-    Name: just_txt
+    Children: []
     ClassName: StringValue
+    Id: id-2
+    Metadata:
+      ignoreUnknownInstances: false
+    Name: just_txt
+    Parent: ~
     Properties:
       Value:
         Type: String
         Value: "Hello, world!"
-    Children: []
-    Metadata:
-      ignoreUnknownInstances: false
 messageCursor: 0
 sessionId: id-1