Fixes #5 - Update home page hero unit

## Background 

https://gitlab.com/eyeo/websites/web.adblockplus.org/issues/5

## Technical details

- This patchset applies to the index_page branch of web.adblockplus.org
- This patchset is a work-in-progress as it's specification is incomplete
- This draft implements the no-script state of this section
- Implementation of this section includes the implementation of the base page (switching from one page per browser to *just* one page)
- The video component has been developed further in the master branch, as a result I have left it as-is until I rebase and replace it later

[juliandoucette, 2018-03-07 20:11:18]

Hey Manvel! :)

I added you as a reviewer - but you should probably hold off for now. I have
only implemented the no-js state so far, and I will make responsive changes live
with product soon as-needed. Sorry for the notification. I just thought that it
would be useful to upload this now to have something to show and backup/document
the first draft of this somewhat complex change.

I may go ahead and push a future revision of this change without approval in
order to rebase and fix dependencies easier and then have Ire review the results
before we merge this branch into master when the index page is ready to launch.

(Ire is on vacation this week.)

[juliandoucette, 2018-03-09 14:35:53]

Done https://hg.adblockplus.org/web.adblockplus.org/rev/1d8bf7725f3b.

I met with Jeen 1 on 1 to demo this change and discuss outstanding issues with
this section and others on this page. I have complied her suggestions into a
document that I will now convert to one or more tickets and address separately
using this change as a base.

Detail: The merge change that follows this one provides an updated video
component for this section.