v2.0.0 -> v2.1.0

Features

• e494bd9 wal-e: use the latest wal-e to use aws instance profiles

Fixes

• 8bfc4ee contrib: allow 5 or 6 backups
• 419a0e3 rootfs: enable archive_mode before initial boot

Documentation

• 61a4dc9 CHANGELOG.md: add entry for v2.0.0
• 4efe5f9 README.md: Fix the default value of IMAGE_PREFIX