getData
Retrieves a record.
    function(params)
  
  Returns a promise that resolves to the instance data for particular parameters.
The following shows how constructor calls getData
and what it does with the response:
connection.getData({id: 1}).then(function(instanceData){
  connection.hydrateInstance(instanceData);
});
  
  Parameters
- params 
{Object}:A object that represents the set of data needed to be loaded.
 
Returns
 {Promise<Object>}: 
A promise that resolves to the properties of a record.
Use
Extensions like data/url implement getData  but implementing it yourself can be as simple as:
var behavior = connect([],{
  getData: function(params){
    return new Promise(function(resolve, reject){
        $.get("/api/todo",params).then(resolve, reject)
    });
  }
})