Add email validation in Voter addition form

Add validation email in Voter addition form so that whenever it's empty or invalid email, the submit button will remain disabled and tell the user to populate form field with a valid value. Now the button gets enabled only when both the name and email entered is valid.

This change will cover all the corner cases including a case where a user enters an invalid email and add a validation message about the invalid email and also when the name field is unfilled.

This will solve Issue 64

You can view the video of it's working. Email_Validation