Added a Next Workflow on the git section pages

I figured that it would be easier for the instructors to navigate in the workshop content if there was a Next page link at the bottom of each page.

I just did it for the git section pages. If you tell me that it's useful, I'll do it for every section.

Also, I don't know much about Jekyll, but : 
1) Is there a way to right align this without HTML? (If not, I guess that I'll do it with HTML)
2) Maybe it would be worth it to add a previous link also, what do you think?
3) Finally, if there's a way to automatically generate the link from the neighboorhod pages, that would be cool (so that if the title of the page change, the link would change automatically). But I don't know if it's feasible.

Tell me what you think !