observable-prerender-animate Progress Bar

[asg017]

Logs currently look like this

[139/257] Waiting for [ 'update' ]
[139/257] Screenshotting mapSVG
[140/257] Redefining
[140/257] Waiting for [ 'update' ]
[140/257] Screenshotting mapSVG
[141/257] Redefining
[141/257] Waiting for [ 'update' ]
[141/257] Screenshotting mapSVG
[142/257] Redefining
[142/257] Waiting for [ 'update' ]
[142/257] Screenshotting mapSVG
[143/257] Redefining
[143/257] Waiting for [ 'update' ]
[143/257] Screenshotting mapSVG
[144/257] Redefining
[144/257] Waiting for [ 'update' ]
[144/257] Screenshotting mapSVG
[145/257] Redefining
[145/257] Waiting for [ 'update' ]

Something like this would be pleasant:

[=========>                        ]  141/257 - 55%  - Waiting for ['update'] 
[=========>                        ]  141/257 - 55%  - Screenshotting mapSVG
[=========>                        ]  142/257 - 56%  - Waiting for ['update'] 

• https://github.com/visionmedia/node-progress
• https://www.npmjs.com/package/cli-progress
• https://github.com/sindresorhus/p-progress

dont do it if it's too complex or if the progress bar dep is too large.

CLI changes:

op-animate @asg017/sunrise-and-sunset-worldwide graphic \
    --iter-waitfor controller \
    --iter-index \
    --iter timeI:times \
    --out-dir $OUTDIR/frames 

Actually, let's just have animate default to progress bar, and opt-in --verbose that prints progress line-by-line. Since you would print animate results to stdout.... right?