Suppress "No such file or directory - list" message

How to reproduce:

  1. Remove ~/.fluentd-ui/
  2. Run `bin/rails console`
  3. You will see the following output:

         bin/rails: No such file or directory - list
         Loading development environment (Rails 4.1.4)
         irb(main):001:0>
Converge codes for user name restriction

The current implementation accepts only "admin" user. Codes for the
restriction exist in several files.

This change converges codes for the restriction to
app/models/user.rb. This change will be helpful when we support more
user names.
Merge pull request #72 from kou/suppress-list-not-found-message

Suppress "No such file or directory - list" message
Fix to find fleunt-gem command path
Update Gemfile.lock
Fix translation missing at information page.
Fix translation missing at recommended plugins page.
Merge pull request #84 from hassaku/fix_missing_translation

Fix missing translation
Add translation for processing.
Hide install button while processing.
Show processing status.
Add draper gem to decorate a model.
Refactor logic in view using decorator.
Change the priority of checking status because both installed and not installed plugins could be processing.
Add spec for plugin's decorator.
Change status depending on starting plugin install.
Merge pull request #83 from kou/converge-admin-user-restriction

Converge codes for user name restriction
Merge pull request #85 from hassaku/show_processing_status

Show processing status of plugin install