General

- `DRIVER` environment variable now supported to supply value for `create --driver` flag

- Update to Go 1.6

- SSH client has been refactored

Drivers

- `azure`

- Driver has been completely re-written to use resource templates and a significantly easier-to-use authentication model

- `digitalocean`

- New `--digitalocean-ssh-key-fingerprint` for using existing SSH keys instead of creating new ones

- `virtualbox`

- Fix issue with `bootlocal.sh`

- New `--virtualbox-nictype` flag to set driver for NAT network

- More robust host-only interface collision detection

- Add support for running VirtualBox on a Windows 32 bit host

- Change default DNS passthrough handling

- `amazonec2`

- Specifying multiple security groups to use is now supported

- `exoscale`

- Add support for user-data

- `hyperv`

- Machines can now be created by a non-administrator

- `rackspace`

- New `--rackspace-active-timeout` parameter

- `vmwarefusion`

- Bind mount shared folder directory by default

- `google`

- New `--google-use-internal-ip-only` parameter

Provisioners

- General

- Support for specifying Docker engine port in some cases

- CentOS

- Now defaults to using upstream `get.docker.com` script instead of custom RPMs.

- boot2docker

- More robust eth* interface detection

- Swarm

- Add `--swarm-experimental` parameter to enable experimental Swarm features