get actual site screenshot

[jamesros161]

resolves #168

This PR will generate a screenshot of the site just after inspirations installation, to be displayed on the 'My Inspirations' page.

This PR requires the following wpb-assets PR: wpb-assets:#543

Testing instructions:

1. Install and build this branch of inspirations.
2. Point to a dev server that utilizes the proper branch of wpb-assets ( 'https://api-dev-jamesros.boldgrid.com' ) will work as of the writing of these instructions
3. Install an inspiration
4. Verify the screenshot on the My Inspirations page reflects the installation you chose.

[bwmarkle]

I feel like we're adding more complexity than is needed.

We want to show a screenshot of the theme, it doesn't actually have to be the user's site.

During the Inspirations process, we already have screenshots of the websites. To get the theme's screenshot, we should be able to send over the theme + category?

This approach feels much less complicated.