Sometimes we don't want to auto-navigate on zipper create

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Scenario
By default a new zipper will auto-navigate to the first non comment/whitespace node.

This is normally what we want.

But this is not always what we want. For example we don't want this when walking a zipper, we want to hit all nodes so want to start from the root node.

First Idea
Zipper creation functions already have an options map.
Consider adding an option to not auto-navigate.

Maybe :auto-navigate with a default of true (for backward compatibility).

Alternative Idea
Make it dead simple to navigate to top regardless of your current position by adding a top fn to zip API.

[lread]

Newer dupe #189 replaces this issue and proposes a better solution (thanks @mainej!)