Release v0.2.4

This release includes:

• google-v2 provider:
  • --min-ram and --min-core parameters can now be used to automatically select one of the Compute Engine Custom Machine Types.
  • --mount a persistent disk created from a Compute Engine Image
  • Prefixes like "Execution failed: action <n>" removed from status messages in dstat.
• local provider:
  • --mount a local directory
• Add Hong Kong zones.