update return_to before redirect to login

[MattBudz]

Summary

Spec

Currently, when a user is on any view and the session times out, the user is redirected back to the login view. Once logged back in the user goes to projects#show in ce or projects#index in pro.

Besides that, when they are using the editor while timed out, the preview on the right does not reflect their changes. (because they have been logged out). This isn't good UX and would confuse users.

Proposed solution

Return the user back to the page they were on when the session timed out. While the user is on the editor while timed out, show an alert message to inform users to login again

Check List

• [x] Added a CHANGELOG entry