Require "keypress"

"keypress" makes it possible to react directly on keypress events in the
CLI which we want to use for the pause/resume functionality.
Implement pause/resume for downloads

This commit makes it possible to pause an active download by hitting the
spacebar. This just deselects all the currently active files.
Merge github.com:mafintosh/peerflix into pause-resume
Subtract paused time from elapsed time
Draw more often

Makes the pausing and resuming a lot smoother.
Merge github.com:mafintosh/peerflix into pause-resume
Only deselect file that is being streamed back

But deselect all files if running with the `--all` flag
Pause only possible/visible when no player is open

Because when a player is currently connected to the stream pausing won't
work.
Merge pull request #137 from MaxGfeller/pause-resume

Add pause/resume functionality