v2.1.0

Added support for specifying availability_zones, public_subnet_cidrs and private_subnet_cidrs (replaces private_subnet_count), to give more control over the number of public/private subnets and their sizes.

This means that if you are coming from a previous version of this module and had private_subnet_count set to a non-zero value, you will be required to specify your private_subnet_cidrs = [<values>...] when upgrading.