Add tests: links such as "Profile" and "Setting" don't appear when user not signed-in.
$ be rspec spec/requests/authentication_pages_spec.rb
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Finished in 1.11 seconds
22 examples, 0 failures

Randomized with seed 11163
REFACTOR: Organize common form fields by a partial.
Merge branch 'master' of github.com:Tacahilo/sample_app
Redirect to the root URL if signed-in users access the (new|create) actions.
$ be rspec spec/
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Finished in 4.54 seconds
92 examples, 0 failures

Randomized with seed 33189
Use double quotation