Changed version of gem and added Nokogiri to gem dependencies.
Created ability to search for warnings by zip code.

It uses Nokogiri to get the zone code (e.g., NY003) for the specific zip code, then searches for the weather alerts using that code.

Also included an error message in case the gem returns no active alerts.
Removed comments that were put in place for testing purposes.
Merge pull request #4 from nicolejpaz/add_zip_functionality

Add zip functionality