Update spree_zones_by_zip_code.gemspec
Update spree_zones_by_zip_code.gemspec

Rubygems gives a validation error with TODO or FIXME words on gemspec. https://github.com/rubygems/rubygems/blob/8876b4c0b38307142c4f44800f5ad9b85e5ea013/lib/rubygems/specification.rb#L1758
vlledo/spree_zones_by_zip_code,vlledo/spree_zones_by_zip_code,vlledo/spree_zones_by_zip_code