Add More Loaders and Plugins section

[mzgoddard]

Close #29

• Discusses css super set loaders, babel, and baking html
• Exercise with babel and baking html

[gnarf]

@lyzadanger @z - I handle most of the comments lyza mentioned, as well as some of my own in this commit:

https://github.com/bocoup/webpack-workshop/pull/51/commits/e8bcae6bd1fb651c14a04806924990d4012a246d

Figured this was easier than commenting on all these lines :)

[gnarf]

Also, I'm just going to land this... we can sort it out later if there was any further followup!