Add a test for partials referencing paths.

js/test_cases/partial_path/greeting.dust

@@ -0,0 +1 @@
+Hello {name}{?item}, nice {item}{/item}!{~n}

js/test_cases/partial_path/input1.json

@@ -0,0 +1,14 @@
+{
+  "people": [
+    {
+      "name": "Alice",
+      "item": "cat"
+    },
+    {
+      "name": "Bob"
+    }
+  ],
+  "globals": {
+    "item": "couch"
+  }
+}

js/test_cases/partial_path/main.dust

@@ -0,0 +1,3 @@
+{#people}
+{>greeting item=globals.item/}
+{/people}