[GoComics] Update to new website structure

[stjohnjohnson]

GoComics.com has updated their website. The image location is now a
data attribute in a div.

Here is an example from https://www.gocomics.com/lio/2020/02/21:

<div class="comic container js-comic-2952528 js-item-init js-item-share js-comic-swipe bg-white border rounded" data-shareable-model="FeatureItem"
--
  | data-shareable-id="2952528"
  | data-transcript=""
  | data-id="2952528"
  | data-feature-id="162"
  | data-feature-name="Lio"
  | data-feature-code="lio"
  | data-feature-type="comic"
  | data-feature-format="print"
  | data-date="2020-02-21"
  | data-formatted-date="February 21, 2020"
  | data-url="https://www.gocomics.com/lio/2020/02/21"
  | data-creator="Mark Tatulli"
  | data-title="Lio for February 21, 2020 \| GoComics.com"
  | data-tags=""
  | data-description="For February 21, 2020"
  | data-image="https://assets.amuniversal.com/298bf7002b690138e5f1005056a9545d"
  | itemtype="http://schema.org/CreativeWork"
  | accountableperson="Andrews McMeel Universal"
  | creator="Mark Tatulli">

[deathbybandaid]

I just patched my bridge file, and this looks to be working perfectly! Thank You!

[somini]

Can confirm this fixes it, the master branch is broken otherwise. Pinging @RSS-Bridge.

The fail on Travis is unrelated, the fix is on #1458 .

[teromene]

Thank you for the fix !