Add integration test for add_field with $last wildcard

#102

Behaviour seems to have changed #102 breaks and master ingores
if there is no object in the array and you use to `add_field` with
$last wildcard

Author: TobiasNx

metafix/src/test/resources/org/metafacture/metafix/integration/record/fromJson/toJson/add_fieldkIntoArrayOfObjectsWithLastWildcard/expected.json

@@ -0,0 +1,13 @@
+{
+  "animals" : [ {
+    "name" : "Jake",
+    "type" : "dog"
+  }, {
+    "name" : "Blacky",
+    "type" : "bird",
+    "key" : "value"
+  } ]
+}
+{
+  "animals" : [ ]
+}

metafix/src/test/resources/org/metafacture/metafix/integration/record/fromJson/toJson/add_fieldkIntoArrayOfObjectsWithLastWildcard/input.json

@@ -0,0 +1,15 @@
+{
+  "animals" : [
+    {
+      "name": "Jake",
+      "type": "dog"
+    },
+    {
+      "name": "Blacky",
+      "type": "bird"
+    }
+  ]
+}
+{
+  "animals" : [ ]
+}

metafix/src/test/resources/org/metafacture/metafix/integration/record/fromJson/toJson/add_fieldkIntoArrayOfObjectsWithLastWildcard/test.fix

@@ -0,0 +1 @@
+add_field("animals[].$last.key", "value")

metafix/src/test/resources/org/metafacture/metafix/integration/record/fromJson/toJson/add_fieldkIntoArrayOfObjectsWithLastWildcard/test.flux

@@ -0,0 +1,8 @@
+FLUX_DIR + "input.json"
+|open-file
+|as-records
+|decode-json
+|fix(FLUX_DIR + "test.fix")
+|encode-json(prettyPrinting="true")
+|write(FLUX_DIR + "output-metafix.json")
+;