Rewrote GregMefford's sections on Layers 1,2,3 and fixed a typo or two
More rewites on networking_101
Added initial content for networking_201
Added term 'VLAN' to glossary.rst
Fix formatting on VLAN entry in glossary.rst
Made changes as recommended by @miketheman on reviewing prior push
Made add'l changes as recommended by @miketheman on review, made some new edits, and added some new material
Merge branch 'master' of https://github.com/wdennis/curriculum into wdennis-master
fix a few typos and style conforms.