[refactor] Location of image files and internals bug fix

[Polaris000]

While fixing issue #57, I had n't noticed that images were present in the assets folder. Thus, I created an images folder just to store the favicons for the site. I think it would be a great idea to move everything to one place: either to the assets folder or to the images folder.

Also, the README in the internals folder leads to the creation of this page when the site is generated. This causes a problem when users navigate away from this page, since the relative base url now ends with a /internals, leading to page not found errors.

I think the README should be deleted to fix this problem.

[Polaris000]

Please have a look @jgbarah, whenever covenient!

[vchrombie]

This issue is handled in the new version of the tutorial https://github.com/chaoss/grimoirelab-tutorial/pull/178

[fioddor]

I believe this PR can be closed.

cc:@sduenas