Fixed knobs-addon performance issues

[Gongreg]

Issue: #809 Add throttling/batching of updates for addon-knobs.

Fixing performance issues

Added timestamps to setKnobs event.

If user is typing, his typing shouldn't be interrupted by randomly happening setKnobs action. Now setKnobs will actually do something only after user finishes typing.

Example

const {withKnobsOptions} = require('storybook-addon-knobs');
story.addDecorator(withKnobsOptions({timestamps: true}));

Added ability to pass debounce option when adding decorator

As #92 said we needed an option to add debouncing to knob changes.
I added an option to pass options when adding decorator to story.

Example

const {withKnobsOptions} = require('storybook-addon-knobs');
//debounce options are wait and leading, same as in lodash.
story.addDecorator(withKnobsOptions({debounce: { wait: 100, leading: true}}));

Difference between these two updates

The first update timestamps solves issues that happen when developing locally, since sometimes setKnobs happened after user has already started typing and it reverted the typing.
The debounce is useful if you are using knobs over the air, in device or in separate server, it simply doesn't send so many requests.

Of course you can use both at the same time:

const {withKnobsOptions} = require('storybook-addon-knobs');
//debounce options are wait and leading, same as in lodash.
story.addDecorator(withKnobsOptions({
    debounce: { wait: 100, leading: true},
    timestamps: true
}));

Things to note

• Added loadash.debounce package as a dependency.
• Two tests changed, added timestamps so they would work.

How to test

See examples above.

[codecov]

Codecov Report

Merging #1039 into master will increase coverage by 0.15%.
The diff coverage is 63.33%.

@@            Coverage Diff             @@
##           master    #1039      +/-   ##
==========================================
+ Coverage   12.74%   12.89%   +0.15%     
==========================================
  Files         199      199              
  Lines        4472     4489      +17     
  Branches      711      714       +3     
==========================================
+ Hits          570      579       +9     
- Misses       3272     3278       +6     
- Partials      630      632       +2

Impacted Files	Coverage Δ
addons/knobs/src/index.js	0% <0%> (ø)	⬆️
addons/knobs/src/components/WrapStory.js	11.11% <0%> (-0.16%)	⬇️
addons/knobs/src/KnobManager.js	39.13% <50%> (+0.32%)	⬆️
addons/knobs/src/components/Panel.js	88% <85.71%> (-4.31%)	⬇️

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[ndelangen]

@Gongreg do you need help rebasing?

[danielduan]

+1 lgtm, looks like it would definitely help for props that trigger big dom changes. thanks for the PR @Gongreg !

[Gongreg]

@ndelangen Just like we talked in slack, if you could rebase it would be cool :)

[ndelangen]

I will rebase this for you.

[ndelangen]

rebased !

[danielduan]

I'm in favor of fixing the lint issues: var => const, extra parenthesis, etc. Otherwise, I think its good to go.

Actually scratch that, they're already existing so don't worry about it. Let's get this in the next alpha?