Scaffolding for local create

[SoManyHs]

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Testing

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[SoManyHs]

make && make test pass.

~/go/src/github.com/aws/amazon-ecs-cli(local-create)$ ecs-cli local create --help
NAME:
   ecs-cli local create - Uses a Task Definition input and converts it to a docker-compose.local.yml file that can be run locally.

USAGE:
   ecs-cli local create [command options] [arguments...]

OPTIONS:
   --file value, -f value    The file name of the task definition to convert.
   --arn value, -a value     The ARN of the task definition to convert.
   --output value, -o value  The name of the file to write to. If not specified, defaults to docker-compose.local.yml
   

~/go/src/github.com/aws/amazon-ecs-cli(local-create)$ ecs-cli local create
foo // placeholder output

[efekarakus]

Looks good! just two small nit comments. Feel free to merge after addressing them.