`buildMessage` function is backwards incompatible

## Version

Latest Master starting at #126

## Test Case

## Steps to reproduce

## Expected Behavior

From the Docs and existing behavior the `buildMessage` function should have a signature like this:
`buildMessage(key, type, value, context = {})`.

## Actual Behavior

On [this line](https://github.com/DockYard/ember-changeset-validations/blob/master/addon/utils/validation-errors.js#L17) the signature made a backwards incompatible change and now looks like this: `buildMessage(key, result)`.

Is the next release intended to bump the major version? If not, any apps relying on `buildMessage` will be broken.