Release 1.6.0

• Per-identity deduplication and tags migrations in the no_duplicate plugin.
• New init_status plugin.
• Use the improved concurrent insertion of PostgreSQL 9.5 when available.
• Bugfixes on invalid utf-8.

Release 1.5.0

• add workaround for a DBD::Pg 3.x bug with utf-8 handling
• reimplement rfc2047 encoding for consecutive words
• replace tab by space in multi-line headers
• fix utf-8 encoding in html mime parts
• fix undesirable CRLF conversion in attachments on MS-Windows