Top performers Mark2: Storage + Yosemite fmwk support

[bummytime]

This PR adds support for Top Earners in Storage and Yosemite.

Storage

2 new Storage entities were added: TopEarnerStats and TopEarnerStatsItem:

In addition, the data model is now versioned (Model 2) and a light migration should take place for this change. To help matters going forward, I added Storage/Storage/Model/MIGRATIONS.md to help us keep track of and changes to the data model (just like WPiOS).

Yosemite

In the Yosemite fmwk, StatsStore and StatsAction were updated to handle top earners network + storage logic (via retrieveTopEarnerStats()).

Also, I added a bunch of unit tests to support all of this new logic 👆👆👆.

Ref: #178

Testing

No UI to test this out yet, so verify the unit tests are ✅ and the code looks acceptable.

@jleandroperez would you mind taking a peek?

[wpmobilebot]

	1 Warning
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

Generated by 🚫 Danger

[jleandroperez]

Perfect. End to end!!!

Awesome work Matt!!!

[jleandroperez]

Nice!!!!!

[peril-woocommerce]

	Fails
🚫	Danger failed to run /app/danger-0.o6vtsm2yakf.ts.

	Warnings
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

Error TypeError

Cannot read property 'diff' of null
TypeError: Cannot read property 'diff' of null
    at checkCommitDiffs (/app/danger-0.o6vtsm2yakf.ts:43:49)
    at process._tickCallback (internal/process/next_tick.js:68:7)

Dangerfile

38|         if (git === undefined) {
39|             console.log("About to crash due to an error")
40|             console.log("File:", thisFile)
41|             console.log("Danger Object: ", danger)
42| 
---------------------------------------------------^
43|             if (danger !== undefined) {
44|                 console.log("Danger is no longer defined")
45|             }
46|             else {

Generated by 🚫 dangerJS