target nodejs v8 (BREAKING)

This adds support for async/await. Prior to this patch, transpiled code
using these features had references to "regeneratorRuntime", which gives
errors at runtime when used in Fuse apps since "regeneratorRuntime" is
not defined there.

Node.js v8 uses V8 v5.8, which is older than the version(s) we're
currently using in Fuse apps, so it's fairly safe to assume that all
JavaScript features used by transpiled code are supported in Fuse.

Author: mortend

src/server.js

@@ -24,13 +24,21 @@ function transpile(filename, code) {
         babel_plugin_proposal_object_rest_spread,
         babel_plugin_proposal_optional_chaining
     ]
+    const target = [
+        babel_preset_env,
+        {
+            "targets": {
+                "node": "8"
+            }
+        }
+    ]
 
     if (ext == "ts") {
         return babel.transform(code, {
             filename: filename,
             presets: [
                 babel_preset_typescript,
-                babel_preset_env
+                target
             ],
             plugins: plugins,
             sourceMaps: "inline"
@@ -39,7 +47,7 @@ function transpile(filename, code) {
         return babel.transform(code, {
             filename: filename,
             presets: [
-                babel_preset_env
+                target
             ],
             plugins: plugins,
             sourceMaps: "inline"