Create a web-based tool to show predicted differences

[marco-c]

The tool should be similar to the labeling tool, but only show images for which we predict there are differences.

We should have a button to file an issue on webcompat.com, and a button to say that the images are not different.

[marco-c]

After this, we can move the labeling tool to be web-based too.

[marco-c]

In the first iteration, we will just show images that we have predicted already (using a crawler, we will daily collect screenshots and perform the prediction, the web-based tool will only show the results). The user will be able to either click on "Create webcompat.com issue", which opens a link to open an issue in webcompat.com prefilling only the title, or on "Not different".

Then we will:

• Add the possibility to navigate to websites (#277);
• Make "Create webcompat.com issue" actually prefill an issue with screenshots too (#276).