Fix build
Fix build

When running `bundle exec rake db:setup` in Travis we were getting an error
related to the Geozones table not being present yet. It was being called
to define geozone segements using dynamically generated class methods[1]

With this commit we are checking if the geozone's table exists before
creating geozone segments, which should hopefully fix the build

[1] https://github.com/AyuntamientoMadrid/consul/pull/1579

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