Geonamescache Versions Save

• More consistent behavior of search_cities function. By default the attribute value is search for partial matches and search is performed case insensitive. This is different from the previous behavior, where list values were treated differently from string values and search was case sensitive by default. See issue 38. The new behavior was implemented by Chris Pigden @pigden.
• Update geo data.

• Update GeoNames data
• Fix data test name, contributed by @m-gaster

• Use os module and open function in _load_data instead of importlib.resources for compatibilty with Python 3.8, implemented by Benny Elgazar @Bennyelg

• Include 4 different sized city datasets, that can be accessed via the new min_city_population parameter when creating a GeonamesCache class object.

• Add case_sensitive parameter in the search_cities function and the functionality to do case insensitive search implemented by Chris Pigden @pigden
• Update geo data
• Upgrade dependencies
• Only support currently supported Python version 3.7, 3.8, 3.9, i.e. no more Python 2.7 support

• Add alternatenames attribute to entries in cities.json with a list of alternate city names.
• Add search_cities function which returns a list of entries that include the query in given attribute.

Adds admin1code to cities.json. Thanks to Matt Webb (@genmon) for adding this feature.