Revamp "Build a Node" guide

[valentinewallace]

• Make all the overall steps Headers rather than checkboxes
• Make all the information visually hierarchical -- all information/code samples that fall within the header should be indented hierarchically
• Make key-value information more visually keyed-/value'd. i.e. "Dependencies: ChannelManager" becomes "Dependencies: ChannelManager
• All code things that are currently formatted like: "channel manager," "peer manager" should become ChannelManager, PeerManager (i.e. code format all the things)
• Parts of the code samples that are formatted like "<insert X code here>" should be in comments, and prefixed by TODO so syntax highlighting highlights them
• Don't combine multiple examples into the same code sample, split them
• Reorder the information in each step of Setup to be: 1. description, 2. code example, 3. dependencies, 4. references.
• 80col all code examples and comments therein