Fixes error-related bugs and adds specs

* Added poltergeist for JS request specs
* Improved styles for error messages
* Fixed error highlighting in forms with errors
* Fixed incorrect user in dream preview
* Add more rows to the text_area
* Removed unused :inactive_user? method
* Bumped coverage threshold
* Added spec for dream validation failure
* Added spec for editing a dream
* Added spec for previewing a dream
* Added specs for all types of dream lists