Add onPasswordChangeGoTo option

Adds the new, optional 'securesocial.onPasswordChangeGoTo'
configuration property to allow the developer to set which page
the Password Change form should redirect to.

If not set, it preserves the current default option of staying in the
Password Change page.

This option is similar to existing options such as onSignUpGoTo and
onResetPasswordGoTo.
Merge pull request #328 from fernandoacorreia/onPasswordChangeGoTo

Add onPasswordChangeGoTo option