Changes:

* Make epgsql commands pluggable  (see [pluggable_commands.md](pluggable_commands.md)).
  Now we are not limited only by API functions provided by epgsql (equery/squery/prepared_query etc),
  but may create own commands as a plugins. Still, understanding of PostgreSQL network protocol needed
  to be able to do so.
* Make epgsql datatype encoding/decdoding pluggable (see [pluggable_types.md](pluggable_types.md)).
  Now we are able to add or tweak codecs for existing as well as custom PostgreSQL
  datatypes (like datetime, varchar, enum, arrays etc).
  XXX: Highly recommend to add `{codecs, []}` option to your `epgsql:connect/X` calls if you don't use
  PostGIS and hstore datatypes: this will reduce connection setup time.
* epgsql internals had a huge refactoring (4,000 additions and 1,750 deletions for ~5500 LOC project).
  Code now is much more modular, documented and have a lot of internal typespecs. Performance
  improvements are also expected.
* Now we try to use iolists as much as possible and avoid binary and string concatenations when ever possible.
  Expect noticeable performance improvements for large BYTEA / TEXT / VARCHAR / JSON / JSONB etc fields.
* Extended and documented `epgsql:with_transaction/3`.
  Now it's possible to preserve original exception's stacktrace, finally!
* macaddr and macaddr8 datatypes support added
* Float datatype support was extended with `nan`, `minus_infinity`, `plus_infinity`
* elvis code style check was added to our travis pipeline
* Brand-new PostgreSQL 10 scram-sha-256 auth method added
  (see https://www.postgresql.org/docs/10/static/auth-methods.html#AUTH-PASSWORD and
  https://www.postgresql.org/docs/current/static/sasl-authentication.html)
* A lot of typespecs were rewritten and lots of internal typespecs were added

Incompatibilities:

* Some unexpected performance issues may appear, but we expect performance improvements, especially
  for a large result sets (when a lot of rows are returned by a query) and for large string/json/blob
  query parameters
* Undocumented `epgsql:update_type_cache/2` API was changed
* A lot of typespecs were updated. Some typespecs were deprecated or moved from epgsql.erl to other
  modules. So, some new dialyzer warnings might pop-up
* Some new error messages might be returned, especially from epgsql:connect/X functions
* Memory consumption per-connection might slightly grow because we maintain per-connection OID<->codec
  mapping table, which might be quite big in some cases. This also may produce bigger error_logger
  reports in case of epgsql connection process crashes.
* Some exported .hrl files have been changed. `#column{}` and `#statement{}` record definitions were extended.
* PostGIS users might be affected by cleanup of ewkb.erl and epgsql_geometry.hrl
* Streaming replication users should pay extra attention. No tests were broken, but a lot of
  modifications were made to this code.
* Passing integer / atom / float as a value of a text / varchar / bytea query parameter is now
  deprecated (so, `epgsql:equery(C, "SELECT $1::text", [my_atom])` will still work but is not recommended)
* Redshift and CockroachDB users might expirience some problems. Please, report bugs!
This tag has no release notes.