wrap non-arrays/strings/falsys in an array in util.list - fixes babel/babelify#69

src/babel/util.js

@@ -59,8 +59,10 @@ export function list(val: string): Array<string> {
     return [];
   } else if (Array.isArray(val)) {
     return val;
-  } else {
+  } else if (typeof val === "string") {
     return val.split(",");
+  } else {
+    return [val];
   }
 }