allow string zipcodes
Update README and docs to indicate that zips are strings
Update rubocop to version 0.20.0
Update .gitignore
Merge pull request #17 from drinks/allow-string-zipcodes

Allow string zipcodes in districts_locate
Bump version to 0.2.3
Update faraday_middleware dependency to ~> 0.9.1
Test against latest Ruby 2.1 release
Update rubocop dependency to >= 0.23