PR for 0.2.4 release

[wnojopra]

This release includes:

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