Update CHANGELOG
Merge branch 'master' of github.com:mitchellh/packer into fix#536

Conflicts:
	CHANGELOG.md
packer: don't panic if can't write to UI
Merge pull request #558 from fabiang/virtualbox-sata

builder/virtualbox: arguments Prefix (--) was missing for (sata)portconfig
Merge pull request #550 from mitchellh/fix#536

builder/amazon/ebs: Add config for target AZ.
builder/amazon: rename availzone to availability zone
builder/amazon/instance: support AZ here too
website: remove extra period.
spelling mistake in comments
Added missing close-curly-brace to default value of execute_command.
Merge pull request #564 from mmercer-appneta/master

Added missing close-curly-brace to default value of execute_command in Chef Solo docs
Merge pull request #572 from ktruong7/format-issues1

Spelling mistake in comments
s/extremely to/extremely easy to/
Merge pull request #575 from ciarand/feature/fix-typo

Fix typo in documentation
builder/amazon/*,builder/openstack: properly scrub sensitive [GH-554]
communicator/ssh: buffer file on disk to read length [GH-561]
builder/virtualbox: allow disabling guest addition uploading
website: docs on disabling guest additions
command/fix: add fixer to auto set guest_additions_mode
update CHANGELOG