Fix Broken Images in HTML docs

[rpalcolea]

This is a fix for #58

Rearranges images into a proper subfolder and modified build file to generate proper HTML docs.

[rpalcolea]

The build stopped:

-- Test testFindByUsername(spec.UserSpec)
No output has been received in the last 10 minutes, this potentially indicates a stalled build or something wrong with the build itself.

[rpalcolea]

Hi @burtbeckwith

Well after a few attempts, the Travis CI build hangs up. It happens in different tests

-- Test testUniqueName(spec.AclSidSpec)
No output has been received in the last 10 minutes, this potentially indicates a stalled build or something wrong with the build itself.

You can see the history of the builds for the pull request, always on different steps. I don't expect this to break the build.

[sdelamo]

Problems with screenshots was they were not being copied to Github pages branch. Thanks for this pullrequest @rpalcolea however I am not going to merge it for now. The issue is fixing is already fixed