add includeRegenerator option

lib/6to5/file.js

@@ -48,21 +48,22 @@ File.normaliseOptions = function (opts) {
   opts = _.cloneDeep(opts || {});
 
   _.defaults(opts, {
-    experimental: false,
-    reactCompat:  false,
-    playground:   false,
-    whitespace:   true,
-    moduleIds:    opts.amdModuleIds || false,
-    blacklist:    [],
-    whitelist:    [],
-    sourceMap:    false,
-    optional:     [],
-    comments:     true,
-    filename:     "unknown",
-    modules:      "common",
-    runtime:      false,
-    code:         true,
-    ast:          true
+    includeRegenerator: false,
+    experimental:       false,
+    reactCompat:        false,
+    playground:         false,
+    whitespace:         true,
+    moduleIds:          opts.amdModuleIds || false,
+    blacklist:          [],
+    whitelist:          [],
+    sourceMap:          false,
+    optional:           [],
+    comments:           true,
+    filename:           "unknown",
+    modules:            "common",
+    runtime:            false,
+    code:               true,
+    ast:                true
   });
 
   // normalise windows path separators to unix

lib/6to5/transformation/transformers/es6-generators.js

@@ -1,3 +1,9 @@
+var regenerator = require("regenerator");
+
 exports.ast = {
-  before: require("regenerator").transform
+  before: function (ast, file) {
+    regenerator.transform(ast, {
+      includeRuntime: file.opts.includeRegenerator && "if used"
+    });
+  }
 };