Remove uchiwa::api and pass API data via class params

The puppet-uchiwa module doesn't produce a clean puppet run unless a user defines at least one uchiwa::api.

It would be ideal if the module could define default parameters over-writable by the user, for example by using hiera.

For these two reasons, I changed the module's current structure, replacing `uchiwa::api` with an array of hashes, passed to the `init.pp` class.

In other words, what the user could achieve by declaring...:

```puppet
uchiwa::api { ' API 1':
  host    => '10.56.5.8',
}

uchiwa::api { 'API 2':
  host    => '10.16.1.25',
  ssl     => true,
  port    => 7654,
  user    => 'sensu',
  pass    => 'saBEnX8PQoyz2LG',
  path    => '/sensu',
  timeout => 5000
}
```

...now they can achieve by passing an array of hashes to the uchiwa class declaration:

```puppet
class { 'uchiwa':
  sensu_api_endpoints  =>  [{
                              name => 'API 1',
                              host   => '10.56.5.8'
                              },
                              {
                              name => 'API 2',
                              host => '10.16.1.25',
                              ssl    => true,
                              port   => 7654,
                              user  => 'sensu',
                              pass  => 'saBEnX8PQoyz2LG',
                              path   => '/sensu',
                              timeout => 5000,
                           }],
}
```

Or data can be overwritten by hiera:

```yaml
uchiwa::sensu_api_endpoints:
  - name: 'API 1'
    host: '10.56.5.8'
  - name: 'API 2'
    host: '10.16.1.25'
    ssl: true
    port: 7654
    user: 'sensu'
    pass: 'saBEnX8PQoyz2LG'
    path: '/sensu',
    timeout: 5000
```

If `$sensu_api_endpoints` is not populated when including the class, then the default params defined in `params.pp` will be used:

```puppet
  $sensu_api_endpoints  = [{
                            name      =>  'sensu',
                            host      =>  '127.0.0.1', 
                            ssl       =>  false,
                            insecure  =>  false,
                            port      =>  4567,
                            user      =>  'sensu',
                            pass      =>  'sensu',
                            path      =>  '',
                            timeout   =>  5000,
                          }]
```

If a hash lacks of some params, the defaults are used instead. For example, if we include the uchiwa class above defined in the puppet catalog, the `uchiwa.json` file will look like this:

```json
{
"sensu": [
    {
      "name": "API 1",
      "host": "10.56.5.8",
      "ssl": false,
      "insecure": false,
      "port": 4567,
      "user": "sensu",
      "pass": "sensu",
      "path": "",
      "timeout": 5000
    },
    {
      "name": "API 2",
      "host": "10.16.1.25",
      "ssl": true,
      "insecure": false,
      "port": 7654,
      "user": "sensu",
      "pass": "saBEnX8PQoyz2LG",
      "path": "/sensu",
      "timeout": 5000
    }
  ],
  "uchiwa": {
    "host": "localhost",
    "port": 3000,
    "user": "",
    "pass": "",
    "stats": 10,
    "refresh": 10000
  }
}
```

This PR introduces incompatible changes with previous versions of puppet-uchiwa. Unfortunately leaving both methods of passing the sensu API endpoint params turned out not to be a very trivial task.

Since we don't make use of it, I removed the `richardc/datacat` dependency from the module.

I have also added relevant beaker tests and updated the documentation.