Change the default href for a tag in link_to_add helper.

When isn`t placed the href option to link_to_add helper. It set the default "javascript:void(0)".
But when you use Capybara with RSpec, and use the click_link and pass the content of link, it returns an error. When the href option in link_to_add to '#',  it works. So my opinion its good make the default '#' which work with tests with rspec.