v1.7.0

Added
=====

- Support JSON serialization and deserialization of primitive atomic types.
- Support Text marshalling and unmarshalling for string atomics.

Changed
=======

- Disallow incorrect comparison of atomic values in a non-atomic way.

Removed
=======

- Remove dependency on `golang.org/x/{lint, tools}`.

add atomic duration type (#37)

wrapper around existing `Int64` type for atomic operations on `time.Duration` values