Escape translations and interpolated values

We should always assume that translations and the interpolated values
that are placed into that translation are malicious. This PR will escape
any html within these by default. You may unescape interpolated values
using the `unescape` option.
This paragraph is kind of big. It is good to follow a `summmary` + `body` approach for the first few lines. In this case, code speaks louder than words

-----------------

Add translation support to Express

```
// Define translations via JSON
{
  "welcome": "Welcome to your dashboard!"
}

// Leverage `req.t()` in controllers and `res.locals.t()` in templates
var welcomeText = req.t('welcome'); // Welcome to your dashboard!
<p><%= t('welcome') %></p> // <p>Welcome to your dashboard!</p>
```