Prettier creation error output

[danopia]

If a stack can't be created for some reason, boondoggle dumps raw JSON at the user, like so:

$ boondoggle [ . . . ]
Could not create stack
{"Error":{"Code":"ValidationError","Message":"Template format error: Unresolved
    resource dependencies [Things] in the Resources block of the template",
    "Type":"Sender"},"RequestId":"[redacted]"}