Fixed Circle CI configuration for Bundler config path

Prevents the following deprecation warning:

    [DEPRECATED] The `--path` flag is deprecated because it relies on
    being remembered across bundler invocations, which bundler will no
    longer do in future versions. Instead please use `bundle config set
    path 'vendor/bundle'`, and stop using this flag.

circle.yml

@@ -48,7 +48,7 @@ jobs:
           name: Bundler Install
           command: |
             gem update --system
-            bundle install --path vendor/bundle
+            bundle config set path "vendor/bundle"
 
       - type: cache-save
         name: Bundler Store