feature init csv (#594)

* init csv feature + test

* fmt fixes

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

@@ -0,0 +1,19 @@
+---
+source: tests/tests/build.rs
+assertion_line: 100
+expression: contents
+---
+<roblox version="4">
+  <Item class="LocalizationTable" referent="0">
+    <Properties>
+      <string name="Name">init_csv_with_children</string>
+      <string name="Contents">[{"key":"init.csv","values":{}}]</string>
+    </Properties>
+    <Item class="LocalizationTable" referent="1">
+      <Properties>
+        <string name="Name">other</string>
+        <string name="Contents">[{"key":"other.csv","values":{}}]</string>
+      </Properties>
+    </Item>
+  </Item>
+</roblox>

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

@@ -0,0 +1,6 @@
+{
+  "name": "init_csv_with_children",
+  "tree": {
+    "$path": "src"
+  }
+}

rojo-test/build-tests/init_csv_with_children/src/init.csv

@@ -0,0 +1,2 @@
+Key
+init.csv

rojo-test/build-tests/init_csv_with_children/src/other.csv

@@ -0,0 +1,2 @@
+Key
+other.csv