Change PlayPause to SpaceBar.

This will free up 'p' to be used for pasting below.
Add ability to paste above and below current line.

Uses 'P' and 'p' to paste above and below the current line,
respectively. Sets a template for the PasteBuffer function that takes
an integer: 1 for below, 0 for above.
Add scrolling with paste.

Also use existing enums instead of creating new ones. Added a check for
empty playlist.
Merge pull request #37 from connermcd/paste-above-below

Paste above below