Rename to DoccoViewer

[waldyrious]

Name given on the slideshow, which points to this repo as the source.

Also, from #3:

name that the doccoviewer

@jeromeetienne please clarify if you meant to have two separate projects. IMHO it makes sense to have the entire proeject under the same umbrella, especially since "docco.js" is a very generic and nondescript name that doesn't facilitate discovery of this project.