Follow Prototype: Users being followed and their activities

    Adds the ability to display members that the current user is following and their activites.
    Activity's icons are now displayed using css instead of an tag.

This pr was based on https://github.com/natgeo/modules-activitystream/pull/12/
@Chuwiey you mentioned on PR https://github.com/natgeo/modules-activitystream/pull/12 that I should include this on the private repo. I'm agree with that. 
But in order to do that, we should reoganize the symlinks. We'll have to delete app/styles, and create symlinks for all files insde of it, except for styles/scss/blocks/_activitycaption.scss.
I propose: creating a new scss file in the private repo which includes styles/scss/main.scss and allow us to add more styles. Thoughts?