add button css styles to the links.
all of vaf elements are required.
the select boxes of vaf do not allow blank.
add 2 gems such as 'capybara' and 'capybara-webkit'.
add 'selenium-webdriver' gem.
use the capybara with rspec.
add 'database_cleaner' gem.
add the configuration to use database_cleaner.
write the request spec for signin.