Configure Flask-Mail

Import Message and Mail from Flas-Mail (flask.ext.mail)
Create instance of Mail and configure with riverdots
credentials.

Email account: pruebas@riverdots.com
Add code for sending the email

Add code in routes.py to send the email when the contact form
is filled without any errors.

Email gets send to:
    - alvarosanchez@riverdots.com
    - pruebas@riverdots.com
    - sender email (to get a copy)

Email is sent from:
    - sender email
    - it is actually sent from the account pruebas@riverdots.com
Add "Thank you" message after sending the email

Change placeholder "Form posted." into a thank-you message.
Render 'contact.html' template sending variable success=True.
If it's True, it renders the thank-you message, if it's False
(or it's not present) it render the contact form (as usually).
Add navigation link to Contact Page

Add a navigation link to the contact page in the layout.html
template.