Fix dashboard link to display all of Your Posts

Quick link on dashboard to show all your posts was linking to
the following URL:

    http://localhost:3000/admin/content?search=search[user_id]%3D1

"search" is expected to be a hash, not a normal query
string key. Link needs instead to send:

    http://localhost:3000/admin/content?search[user_id]=1

Now matches the expected search filter calls also
used in "Manage articles" admin section.

Fixes #110
Merge pull request #116 from randomecho/110-your-posts-quicklink-from-dashboard

Fix dashboard link to display all of Your Posts