No option to do email verification

[mallik482]

Version info

Angular: 1.5.11

Firebase: 3.6.8

AngularFire: 2.3.0

Other (e.g. Node, browser, operating system) (if applicable):

Test case

No method to do email verification of user

Steps to reproduce

Expected behavior

Actual behavior

[Jacob Wenger]

Duplicate of #764.