Pause feature

[henry-brisson]

Calling meter.pause(1000) should pause regeneration for 1 second.

Takes a second parameter with timestamp.

If calling pause and the meter is already paused, clears the previous pause.

Consider adding support for pause increments, where calling pause with an increment does not pause a paused meter, but stacks its paused duration. Perhaps something like: meter.pause({duration: 1000, increment: true}) or not using object destructuring.

Other considerations:

• pause() without parameters may pause the meter forever
• implement resume() to clear any ongoing pauses.