Fixed #11 - Remove -S flag from osm2pgsql call

The -S (--style) flag is unnecessary if we are using the default style file
anyway. The location of this file depends on how osm2pgsql was installed
(for example, in /usr/local/Cellar/osm2pgsql/HEAD/share/osm2pgsql/default.style
or /usr/share/osm2pgsql/default.style).