add outputs command to read outputs

[blake-mealey]

Use case: I want to know the IDs of my developer products/assets/etc for use in game.

Add a rocat outputs [--query <json-query>] [--output <file-path>] to print out a JSON object of the state file's outputs.

Additional use case: I want to automatically digest the IDs in my game with Rojo. Solution: output the data to a JSON file which can be imported into Roblox with Rojo. Need to think about the nicest way to accomplish this with Rojo's current importing methods.

[blake-mealey]

Note this creates a bit of a chicken and the egg problem. We want Rocat to upload the assets and output their IDs, then we want Rojo to build the file, then we want Rocat to upload the changed file. This would require two separate Rocat deploys.

Maybe we should consider separating place file deployments from infra-as-code? (e.g. rocat apply and rocat deploy which could share a state file and utilize the same resource management, but construct different graphs based on the config file)

[blake-mealey]

Closed in #29, but the discussion of making it Rojo-compatible has been moved to #34