Fixes 73 - adds MapQuest credit

Includes MapQuest credit line in the about screen and moves <section>
into partial.
Removes redundant <section>

When <section> was moved into site_info partial, an extra <section> was
erroneously included.
Removes MapQuest logo

The logo was unnecessarily distracting in the about screen and would
require additional code to provide the link behavior correctly. This
commit removes it.
Adds period

This commit adds a period at the end of the MapQuest credit.
Merge pull request #82 from codeforamerica/73_mq_osm_credit

73 mq osm credit