Create Newsletter and add a link to it in the footer

**Is your feature request related to a problem? Please describe.**
We need to update the public and stakeholders as new features are created and we do more things in the community: a newsletter is a great avenue for that as many service providers and people who are interested in reentry use their email primarily over social networks.

**Describe the solution you'd like**
1) Create a mailchimp or alternative newsletter service, not sure how to do this collaboratively, but I @paul-rinaldi needs admin rights or close to that on there
2) Replace this line below in ```footer/index.js``` with the statement Subscribe to our Newsletter for Updates! with a link to the mailchimp sign up/subscribe link (a/href).

**Describe alternatives you've considered**
I haven't considered an alternatives but maybe you know of great ways to communicate about community project / civic tech progress to the community using it? Twitter? @Aycrazy

**Additional context**
See above. I (@paul-rinaldi ) may ask the MSOE honors freshman class to do this.

Inizia leggendo footer/index.js e individua la riga attuale del footer mostrata nell’issue. Decidete insieme un servizio di newsletter, quindi sostituite quella riga con il testo e il link di iscrizione richiesti; il lavoro è completato quando il link del footer porta alla pagina di iscrizione alla newsletter e l’accesso al servizio è stato predisposto.

Scritto dal modello di indicizzazione a partire dal testo della issue.