Change how we present the membership streak to the user

[Orlando Del Aguila]

What: Change how we present the membership streak to the user
Why:
Currently, we do it this way.

We want:

1. Round the time to be months (You have been a member for XX months)
2. Change the word Subscription to be Membership "You have been a member for XX months"
3. Change Subscription to Membership in all translations
4. Prefer i18n instead of hardcoded strings in the app.

How:

• Use Rails' i18n support

[Orlando Del Aguila]

let's revisit this after the launch, I think #165 doesn't implement what is described above