Implement support for turning .json files into Lua modules (#308)

* Stub implementation

* Flesh out feature and add tests. Other snapshots currently failing.

* Blacklist .meta.json in JSON handler

* Write to correct property (Source) instead of Value

* Update changelog

rojo-test/build-test-snapshots/rojo_test__build_test__json_as_lua.snap

@@ -0,0 +1,23 @@
+---
+source: rojo-test/src/build_test.rs
+expression: contents
+---
+<roblox version="4">
+  <Item class="ModuleScript" referent="0">
+    <Properties>
+      <string name="Name">json_as_lua</string>
+      <string name="Source">return {
+	["1invalidident"] = "nice",
+	array = {1, 2, 3},
+	["false"] = false,
+	float = 1234.5452,
+	int = 1234,
+	null = nil,
+	object = {
+		hello = "world",
+	},
+	["true"] = true,
+}</string>
+    </Properties>
+  </Item>
+</roblox>

rojo-test/build-tests/json_as_lua/default.project.json

@@ -0,0 +1,6 @@
+{
+  "name": "json_as_lua",
+  "tree": {
+    "$path": "make-me-a-script.json"
+  }
+}

rojo-test/build-tests/json_as_lua/make-me-a-script.json

@@ -0,0 +1,12 @@
+{
+  "array": [1, 2, 3],
+  "object": {
+    "hello": "world"
+  },
+  "true": true,
+  "false": false,
+  "null": null,
+  "int": 1234,
+  "float": 1234.5452,
+  "1invalidident": "nice"
+}

rojo-test/src/build_test.rs

@@ -31,6 +31,7 @@ gen_build_tests! {
     init_meta_class_name,
     init_meta_properties,
     init_with_children,
+    json_as_lua,
     json_model_in_folder,
     json_model_legacy_name,
     module_in_folder,