Store and compare user email input in lowercase

[weslord]

Current limitations of above two commits:

• If these changes are patched on to an existing project with uppercase emails in the database, those users will no longer be able to login.
• ~Django admin does not use normalize_email in their admin forms, so an admin user could still create or modify users to have emails with uppercase characters.~
• The login page for Django admin does not do any lowercasing, so admin users trying to login with a capitalized email will not be matched to the lowercase version.

[weslord]

Looks like the checks for d5bafb9 failed due to known issue #52

[staydecent]

Looks like the checks for d5bafb9 failed due to known issue #52

I'd be OK with the proxyexample app being commented out by default.