Rename Traits

[f2prateek]

We need a nicer way of renaming special properties that can be defined my multiple keys.

For instance, .created() returns the value of either created or createdAt. This causes inconsistent behaviour.

identify.traits({ createdAt: 'created_at' });
// Ignores created completely

var created = identify.created();
// uses either created or createdAt, whichever is available.

[sperand-io]

When we address this, we should address the following at the same time:

If you use the method name, that will work to get the value, but with an insidious side effect:

identify.traits({ created: 'created_at' });
// uses either created or createdAt, whichever is available.
// but... will leave createdAt there :/