Ignore annotation support

[wata727]

Fixes #142

This PR introduces Ignore Annotation syntax. This annotation can be used to ignore issues that occur on a specific line. Here is an example:

resource "aws_instance" "foo" {
    // tflint-ignore: aws_instance_invalid_type
    instance_type = "t1.2xlarge"
}

Annotations affect only for the same line or the below:

resource "aws_instance" "foo" {
    instance_type = "t1.2xlarge" # tflint-ignore: aws_instance_invalid_type
}

The type of comment does not matter. This means that //, # or /*...*/ can be used. You can also use tflint-ignore: all if you want to ignore regardless of rules:

resource "aws_instance" "foo" {
    /* tflint-ignore: all */
    instance_type = "t1.2xlarge"
}

ToDo

• Add documentation