1. Add the ability for a parsed element to enforce that the line handler not parse any (immediate) child elements of a specified type.
2. Use 1. to allow parsed Url elements to tell the line handler not to parse any child Links or Urls where they are immediate children.

I've built on the functionality of feature 1. in the previous commit to allow non nestables to be asserted indefinitely, or to a specified depth.

This commit serves to add comments detailing parts of the new functionality, and to adjust syntax preferences to match that of the surrounding document. The commit title also now reflects the most significant change made.

Removed granularity controls – elements are assumed to be non nestable indefinitely once declared.

Check if array is empty to shave some performance hits in the case than no non nestables are present.

Swap `under_scores` for `camelCasing`