Do not depend on *read-default-float-format*.

Nota Bene:
1- single-float is actually a loss of precision
   as compared to data available from the feed.
   To fix this must be done in synchronization with cl-geocode.
2- The service used has stopped working just this week with this message:

This USGS data file has been deprecated. To continue receiving updates
for earthquake information you must switch to the new data format
[http://earthquake.usgs.gov/earthquakes/feed/].
In the future, data feeds will be updated and deprecated following our official
deprecation policy [http://earthquake.usgs.gov/earthquakes/feed/policy.php].