Refactor Code Helper Methods

[tselitsk]

• grey out node function
• select neighbor nodes
• highlight node
• is this node a center node or neighbor of center

[bnchdrff]

How could we have a function that selects first-neighbor nodes and their related link and text objects?

This could be used within highlight_neighbor_nodes as well as in the filter-by-year function i'm working on.

[bnchdrff]

After we're done with our current issues, we should step back for a second and try to refactor and restructure... i.e. I don't want to worry about making breaking changes while we're working 😄