Make "n" and "p" focus next/previous entry like in Google Reader. TODO: Doesn't scroll view to keep the current entry visible.
Refactor {open,focus}{Next,Previous}Entry().

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extra : amend_source : f7cbe276ddab8b0838736dc8df4400fb4aebd21f
Merge pull request #153 from kankri/master

Make "n" and "p" keys do what they do in Google Reader