[CSP Report UI] fix of 'InvalidAuthenticityToken' issue
[CSP Report UI] fix of 'InvalidAuthenticityToken' issue

```
I, [2016-04-29T15:24:44.339120 #1973]  INFO -- : Processing by CspReportUriController#report as */*
W, [2016-04-29T15:24:44.339611 #1973]  WARN -- : Can't verify CSRF token authenticity
I, [2016-04-29T15:24:44.340012 #1973]  INFO -- : Completed 422 Unprocessable Entity in 1ms (ActiveRecord: 0.0ms)
I, [2016-04-29T15:24:44.340670 #1973]  INFO -- : ** [Raven] User excluded error: #<ActionController::InvalidAuthenticityToken: ActionController::InvalidAuthenticityToken>
F, [2016-04-29T15:24:44.342385 #1973] FATAL -- :
ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken):
  actionpack (4.2.5.2) lib/action_controller/metal/request_forgery_protection.rb:181:in `handle_unverified_request'
  actionpack (4.2.5.2) lib/action_controller/metal/request_forgery_protection.rb:209:in `handle_unverified_request'
  devise (3.4.1) lib/devise/controllers/helpers.rb:251:in `handle_unverified_request'
  actionpack (4.2.5.2) lib/action_controller/metal/request_forgery_protection.rb:204:in `verify_authenticity_token'
```

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