Bump version number for cache file

Now that the schema has changed (added fts table), we need to start
with a fresh cache.

Fixes #416

lib/Configuration.js

@@ -39,7 +39,7 @@ const DEFAULT_CONFIG = {
   cacheLocation: ({ config }: Object): string => {
     const hash = crypto
       .createHash('md5')
-      .update(`${config.workingDirectory}-v2`)
+      .update(`${config.workingDirectory}-v3`)
       .digest('hex');
     return path.join(os.tmpdir(), `import-js-${hash}.db`);
   },