Use Ruby regex for email validation in guide example
Use Ruby regex for email validation in guide example

existing email regex allowed for invalid emails and invalidated valid emails

- The following emails are shown to be valid emails when they are not:
    - `email_<script></script>_123@example.co.in`
    - `email"123@example.com`
    - `email..123@example.com`
    - `.email123@example.com`
... and a few more

- The following email is shown to be an invalid email when it is valid:
    - `email@123.123.12.123`

Lets use the default ruby regex instead
BlakeWilliams/rails,kmcphillips/rails,Edouard-chin/rails,rails/rails,kddeisz/rails,georgeclaghorn/rails,yawboakye/rails,esparta/rails,kmcphillips/rails,Erol/rails,Erol/rails,kddeisz/rails,yahonda/rails,kddeisz/rails,kmcphillips/rails,Erol/rails,Vasfed/rails,MSP-Greg/rails,BlakeWilliams/rails,MSP-Greg/rails,MSP-Greg/rails,yahonda/rails,kmcphillips/rails,Vasfed/rails,yahonda/rails,yawboakye/rails,yahonda/rails,georgeclaghorn/rails,rails/rails,yawboakye/rails,georgeclaghorn/rails,Vasfed/rails,Erol/rails,Vasfed/rails,BlakeWilliams/rails,Edouard-chin/rails,BlakeWilliams/rails,georgeclaghorn/rails,esparta/rails,esparta/rails,Edouard-chin/rails,kddeisz/rails,Edouard-chin/rails,yawboakye/rails,esparta/rails,rails/rails,MSP-Greg/rails,rails/rails