release-2.0.0

• This is a major release which contains many improvements and some breaking
  changes to the interface, but the changes are fairly straightforward.
• Support for Google Cloud (thanks to @mbookman, @chiniforooshan, @baizhang)
• Support for middleware, event listening and interception, allowing
  CloudBridge to be extended without needing to modify library code (This is
  also potentially useful for handling corner cases for specific clouds).
• The mock provider is now available by default as a standard cloud provider,
  which is useful for testing applications that use CloudBridge.
• Providers now operate in a single zone, and therefore, all methods that
  previously required the zone as a parameter no longer do. Specifically,
  instance.create(), volume.create(), subnet.create(),
  subnet.get_or_create_default() are affected in services,
  and snap.create_volume() is affected in resources. The provider's default
  zone must now be specified through the provider config.
• All exceptions that are generated by CloudBridge will now extend from
  CloudBridgeBaseException
• The cloud package is deprecated and everything under it has been moved
  one level up. For example, instead of
  from cloudbridge.cloud.factory import CloudProviderFactory use
  from cloudbridge.factory import CloudProviderFactory.
• Services are much more uniform now, and sub-services have been introduced
  for greater uniformity. For example, net.create_subnet() is now
  net.subnets.create()
• gateways.get_or_create_inet_gateway() is now simply
  gateways.get_or_create()
• AWS instance types are now served through Amazon CloudFront for better
  performance.
• Miscellaneous bug fixes and improvements.