create .flipper folder

Summary: When no config folder exists, a folder named `.sonar` was created. Instead `.flipper` should be created.

Reviewed By: hning

Differential Revision: D9754717

fbshipit-source-id: 89a7f5c80a9202f448a6bafcf461c941b656c15e

static/index.js

@@ -47,7 +47,7 @@ if (fs.existsSync(flipperDir)) {
   // move .sonar to .flipper
   fs.renameSync(sonarDir, flipperDir);
 } else {
-  fs.mkdirSync(sonarDir);
+  fs.mkdirSync(flipperDir);
 }
 
 const configPath = path.join(flipperDir, 'config.json');