User able to change email with no verification - potential lockout risk with no reset option

[pkparimi]

Severity - (Medium)
Weakness - Violation of Secure Design Principles

Description
User is able to navigate to account settings and change email to any email in a proper email format (i.e. xxxx@xxx.xxx). After clicking 'Save' and submitting the form, this email is now saved as their account email. Subsequently, there is no additional email verification needed unlike when a User signs up. This introduces a potential risk to the user in that they may be locked out of their account with no way to reset their password if the 'new' email is entered incorrectly. Based on the current design the 'updateUser' fuction called on submit here: https://github.com/tidepool-org/blip/blob/develop/app/redux/actions/async.js does not consist of any verification for any updates. At minimum, there should be a verification step when changing email

Steps To Reproduce:-

1. Create a valid account
2. Login to this account
3. Navigate to 'Account Settings' by hitting top right button
4. Change email to any validly formatted email
5. Click 'Save' to submit
6. Logout
7. Try to log in - only the new 'unverified' email will work

Example
Original email - gmail.com used

Saved email that is a 'typo' - gmail.cb is not a valid email host

Logging in with original email does not work

Logging in with this 'typo' email does - with no verification step