tflint: Rules across multiple resources are not supported

Some rules, such as [`aws_cloudwatch_log_group_lambda_retention`](https://awslabs.github.io/serverless-rules/rules/lambda/log_retention/) need to evaluate the relationship between different resources defined in Terraform. Usually, this is done by passing references to other resources. For example, for the aforementioned rule:

```hcl
resource "aws_cloudwatch_log_group" "this" {
name = "/aws/lambda/${aws_lambda_function.this.function_name}
retention_in_days = 7
}
```

The __name__ property above is not known ahead of time, which isn't supported by TFLint. See [this issue](https://github.com/terraform-linters/tflint/issues/571) for TFLint.

## Expected Behavior

Linting terraform files should be able to run with rules that cross-reference resources.

## Current Behavior

__tflint__ fails with an `Unevaluable expression found` error.

## Possible Solution

1. Disable all rules that cross-reference resources.
2. Build that feature for __tflint__.
3. Find another linter for Terraform.
4. Abandon linting for Terraform and implement an alternative solution, such as evaluating resources running on AWS.

I will first disable all rules that cross-reference resources for now, while exploring other solutions.

## Steps to Reproduce (for bugs)
1. Clone the repository and checkout the test/tflint branch
```bash
git clone https://github.com/awslabs/serverless-rules.git
cd serverless-rules
git checkout test/tflint
```
2. Run tests for tflint
```
cd tflint-ruleset-aws-serverless
make test
```
3. Get an error that the expression is unevaluable.

```
Error: Failed to check `aws_cloudwatch_log_group_lambda_retention` rule: Unevaluable expression found in XXX/serverless-rules/tflint-ruleset-aws-serverless/tests/aws_cloudwatch_log_group_lambda_retention.pass.tf:10
```

## Environment

* **Infrastructure as code technology used**:
* **(for `cfn-lint`) Python, cfn-lint, and cfn-lint-serverless versions**:
* **(for `tflint`) Go, tflint versions**:
* **Debugging logs**