Add basic functionality for showing global flash messages.
Add basic styling for global flash messages.
Introduce convenience methods for displaying different types of flash messages.

- `App.alert.status("some message")` – blue flash message
- `App.alert.success("some message")` – green flash message
- `App.alert.error("some message")` – red flash message
Merge branch 'refs/heads/feature/global-flash-messages-170' into prototype
Add custom regions for alerts and modal popups.
Update user & participate controllers to open views in a custom region using reveal.
Update places controller to open views in a custom region using reveal.
Refactor Participate module to better separate concerns between controller and view.
Merge branches 'prototype' and 'feature/extend-region-for-modal-175' into prototype