Remove sequential double quote

I found that in some case sequentila double quotes will cause rspec failure.

For instance, when I run spec with Ruby 2.1.0 on wercker, I got error below.

```sh
Failures:

  1) Post markup default should == "<p>Welcome to Lokka!</p><p><a href=/admin/>Admin login</a> (user / password : test / test)</p>"
     Failure/Error: it { post.body.should == post.raw_body }
       expected: "<p>Welcome to Lokka!</p><p><a href=/admin/>Admin login</a> (user / password : test / test)</p>"
            got: "<p>Welcome to Lokka!</p><p><a href=\"/admin/\">Admin login</a> (user / password : test / test)</p>" (using ==)
     # ./spec/unit/post_spec.rb:56:in `block (4 levels) in <top (required)>'
```

It might be because sequential double quotes apear in `spec/factories.rb`. This pull request deletes them.

For more information, please take a look at [my blog post](http://www.portalshit.net/2014/02/21/how-ruby-treat-sequential-double-quote "Ruby は連続するダブルクオートをどのように扱うか - portal shit!").