Added IGW route for DB subnets (based on #179)

Fix for the error: module.vpc.aws_redshift_subnet_group.redshift: onl…

Fix for the error: module.vpc.aws_redshift_subnet_group.redshift: only lowercase alphanumeric characters and hyphens allowed in name

Read more: https://github.com/terraform-aws-modules/terraform-aws-vpc/issues/180

* Added amazon_side_asn to vpn_gateway

* change to Amazon default ASN (as per API) (#176)

https://docs.aws.amazon.com/cli/latest/reference/ec2/create-vpn-gateway.html

* add vars for custom subnet and route table names

* revert db suffix to "db"

* Add secondary CIDR block support using a local variable to derive the vpc id to ensure the CIDR block operations are applied before the CIDR operations

* Add secondary cidr block outputs to module output

* Add the wonderful examples from matthiasr's PR located at https://github.com/terraform-aws-modules/terraform-aws-vpc/pull/162 all credit goes to them for this wonderful example

* From copy and paste accidentally used variable name that differed from these variables

* Resolve typo in secondary_cidr_blocks

* Fixed README formatting

* Followups for #161

* Added local.vpc_id with description

* Added support for IPv6 to VPC

* Provide separate route tables for db/elasticache/redshift

* Added example for saperate routes

* Updated PR with suggestions

* Make redshift to use separate subnet route table also

* More cleanup and updates

* Fixed one more spelling mistake

just a typo in the docs and in the
public_subnet_tags in the simple example

* Allow tags override for all resources (fix for #138)

* Added tags for all resources which were missing them

Fixed creation of aws_vpc_endpoint_route_table_association when intra_subnets are not set (fixes 137)

* Adding Lambda subnets for serverless functions that need to communicate
within the VPC

* Switched to "infra_subnet" for a private subnet without NAT gateway.

* Fixing typo - removing last "lambda" ref.

* Added README docs on intra subnets, and added it to complete VPC
example.  Fixed naming.

* Initial commit for issue #117

* Adding documentation for NAT Gateway creation

* Adding `enable_nat_gateway` to the documentation

* Updating README.md with `one_nat_gateway_per_az` to be 'true' by default

* Reverted changes back to `one_nat_gateway_per_az` as 'false'

Fixes #82

* Ensures the S3 VPC Endpoint association is only created if there are public subnets

Fixes #89

* Ensures a single DDB association in the public route table

Removed aws_default_route_table and aws_main_route_table_association, added potentially failed example (#111)