From DCist contributor Rebecca Walters: D.C. is mostly a pet-friendly city, specifically a dog-friendly city. In 2003, Purina ranked Washington, D.C., sixth in the Top 50 Pet Healthiest Cities. The city and its suburbs eek out space for dog parks in the midst of burgeoning development to attract pet-lovers looking for a home that offers space for Fido to run. Area residents and their canine friends can be found in the parks, the circles, the…