Fix typos in SYNOPSIS
Make $response->{content} simpler

When the HTTP response content includes only one key, the return value
of the WebService::DigitalOcean method is the only value.

Example:

$do->droplet_list();

The request would return something like:

{
    "droplets": [
        { ... }, // droplet 1
        { ... }, // droplet 2
        { ... }  // droplet 3
    ]
}

The return value of the function will be:

{
    content => [
        { ... }, # droplet 1
        { ... }, # droplet 2
        { ... }  # droplet 3
    ],
    ratelimit => ...,
    is_success => 1,
    # etc
}