Updated py-psycopg2 to 2.7.

What's new in psycopg 2.7
-------------------------

New features:

- Added `~psycopg2.sql` module to generate SQL dynamically (:ticket:`#308`).
- Added :ref:`replication-support` (:ticket:`#322`). Main authors are
  Oleksandr Shulgin and Craig Ringer, who deserve a huge thank you.
- Added `~psycopg2.extensions.parse_dsn()` and
  `~psycopg2.extensions.make_dsn()` functions (:tickets:`#321, #363`).
  `~psycopg2.connect()` now can take both *dsn* and keyword arguments, merging
  them together.
- Added `~psycopg2.__libpq_version__` and
  `~psycopg2.extensions.libpq_version()` to inspect the version of the
  ``libpq`` library the module was compiled/loaded with
  (:tickets:`#35, #323`).
- The attributes `~connection.notices` and `~connection.notifies` can be
  customized replacing them with any object exposing an `!append()` method
  (:ticket:`#326`).
- Adapt network types to `ipaddress` objects when available. When not
  enabled, convert arrays of network types to lists by default. The old `!Inet`
  adapter is deprecated (:tickets:`#317, #343, #387`).
- Added `~psycopg2.extensions.quote_ident()` function (:ticket:`#359`).
- Added `~connection.get_dsn_parameters()` connection method (:ticket:`#364`).
- `~cursor.callproc()` now accepts a dictionary of parameters (:ticket:`#381`).
- Give precedence to `!__conform__()` over superclasses to choose an object
  adapter (:ticket:`#456`).
- Using Python C API decoding functions and codecs caching for faster
  unicode encoding/decoding (:ticket:`#473`).
- `~cursor.executemany()` slowness addressed by
  `~psycopg2.extras.execute_batch()` and `~psycopg2.extras.execute_values()`
  (:ticket:`#491`).
- Added ``async_`` as an alias for ``async`` to support Python 3.7 where
  ``async`` will become a keyword (:ticket:`#495`).
- Unless in autocommit, do not use :sql:`default_transaction_*` settings to
  control the session characteristics as it may create problems with external
  connection pools such as pgbouncer; use :sql:`BEGIN` options instead
  (:ticket:`#503`).
- `~connection.isolation_level` is now writable and entirely separated from
  `~connection.autocommit`; added `~connection.readonly`,
  `~connection.deferrable` writable attributes.

Bug fixes:

- Fixed error caused by missing decoding `~psycopg2.extras.LoggingConnection`
  (:ticket:`#483`).
- Fixed integer overflow in :sql:`interval` seconds (:ticket:`#512`).

Other changes:

- Dropped support for Python 2.5 and 3.1.
- Dropped support for client library older than PostgreSQL 9.1 (but older
  server versions are still supported).
- `~connection.isolation_level` doesn't read from the database but will return
  `~psycopg2.extensions.ISOLATION_LEVEL_DEFAULT` if no value was set on the
  connection.
- Empty arrays no more converted into lists if they don't have a type attached
  (:ticket:`#506`)

(wiz)