Add Core.Anycast field

Merge pull request #23 from ipinfo/uman/anycast

Add Core.Anycast field

Batch ops

Batch operations against the IPinfo /batch API are now supported. See CHANGELOG.md entry for new function list and the API documentation for more details.

CountryName field

A new field CountryName was added to both ASNDetails and Core, which is the full name of the country abbreviated in the existing Country field.

For example, if Country == "PK", now CountryName == "Pakistan" exists.

IPinfo Golang SDK v2.0.0

• The API for creating a client and making certain requests has changed and has
  been made generally simpler. Please see the documentation for exact details.
• go.mod now included.
• All new API data types are now available for the Core & ASN APIs.
• Cache interface now requires implementors to be concurrency-safe.

Initial release

This is a release of the library that users can attach to who don't want to upgrade to v2.0.0, which is going to be the immediate next version.