Upgrade to bengott:avatar 0.6.0

I created a new config file in lib/config/avatar.js (accessible to both client and server) and moved Avatar.options from client/helpers/config.js to the new file. I also configured Avatar to use user initials when none of the linked services can find an avatar (the default behavior). You can change this back to use your default image by editing the config to read:
```
Avatar.options = {
  emailHashProperty: 'email_hash',
  defaultType: 'image',
  defaultImageUrl: 'img/default-avatar.png'
};
```
@SachaG: I also commented out some outdated SCSS/CSS. Like we discussed in the past, I don't wanna rock the boat too much with your Sass compilation workflow, so I'll let you clean that up if you want to.

Whew! This was a big one...