Fix initial view glitch when masonry layout renders

[pierlon]

Summary

Fixes UVP-169.

Checklist

• [x] My pull request is addressing an open issue (please create one otherwise).
• [ ] My code is tested and passes existing tests.
• [x] My code follows the Contributing Guidelines (updates are often made to the guidelines, check it out periodically).

[spacedmonkey]

Number of styling issues here.

• The images are not aligned with the search box.
• Scrollbar needs spacing on the right hand side.
• Space between images is not equal, spacing veritically seems off.
• Need to discuss load in effect with Cathy.

[spacedmonkey]

More weird styling issues on resize.

[spacedmonkey]

Some of the fixes for issues I have found are in #67

[pierlon]

Changes made in https://github.com/xwp/unsplash-wp/pull/66/commits/55db1e637fe6507210ccb9e984998d48e5454703 undo a lot of what was changed before. The images have a set width and height so the browser can pre-render the layout and calculate the aspect ratio for each image.

[spacedmonkey]

This now has a conflict, that needs to be resolved and a unit test added.

Idea would performance be better, we force the images to load when the api response returns. Here is an example of a simple preload function.