Version constraint in subnet,vnet, and remote-state-storage module

the [subnet](https://registry.terraform.io/modules/sjones-sot/subnet/azurerm/0.1.0), [vnet](https://registry.terraform.io/modules/sjones-sot/virtual-network/azurerm/0.1.1), and [remote-state-storage](https://registry.terraform.io/modules/sjones-sot/remote-state-storage/azurerm/0.2.0) modules uses a version constraint that excludes version 0.12.0, referenced below. I had assumed that the version constraint listed was good for versions >= 0.11.1 and < 1.0.0, per this article. This may not be the case. On another note, this module doesn't really seem to add any value to the subnet provider and has no documentation on usage. This issue peeled off of https://github.com/Azure/terraform/issues/16.

```
terraform {
required_version = "~> 0.11.1"
}
```

Inspect the linked subnet, vnet, and remote-state-storage modules and compare their required_version constraints with Terraform 0.12.0 behavior. Confirm the intended version range and update all three constraints if appropriate; done means the modules no longer exclude the referenced version and their usage documentation concern is addressed or clearly separated.

Written by the indexing model from the issue text.