Juju DigitalOcean 0.6.0

• Updated to use DigitalOcean v2 API (Thanks Bruce Frederiksen).
• Use userdata to initialize machines instead of ssh initialization when using v2 api,
  this requires python-jujuclient, and results in significantly faster provisioning (no
  client side waiting for machines to boot and initialie).
• tested with juju 1.24