Add filters_spam attribute and update tests

Correct @spam_count test in submenu view
Add filters spam dependency to gemspec

Add test for marking as spam/ham, from inquiries

Fix bug in test with Actions (id vs class)

Fix mark as spam text (translation)

New tests for the Show and Action links

Login before running tests

Use route helper for the "back to all" path

Create items for individual tests (using let! and factory)

Fix @includes_spam to include_spam?