skytools v3.6

Feature removal:

• Remove ancient compat code from psycopgwrapper:
  • dict* and iter* methods
  • getattr access to fields.
  • Keepalive tuning from connect_database(). That is built-in to libpq since 9.0.
  • Require psycpopg 2.5+

Cleanups:

• Switch C modules to use stable ABI only (abi3).
• Remove Debian packaging.
• Upgrade apipkg to 1.5.
• Remove Py2 compat.