Add validators to forms.py

Add presence validator for all the fields and
add email validator for email field.
Update routes.py with validation code

Add if..else for validating the form. If validation
failed, then send contact form with flash message.
If everything was ok, send placeholder "Form posted".
Add flash messages in contact.html

Add div in contact form template
containing all the flash messages
Add styles to flash messages div in contact.html

Add styles in main.css for message flashing. Red div.
Fix bug in contact.html

Bug: Mispelled get_flash_messages() in template contact.html
It said get_flash_message instead of get_flash_messages. The
final 's' was missing