Version chooser uses latest included version rather than latest online version as default

[nornagon]

To repro:

1. install on fresh machine
2. look at top-left corner for current electron version
3. observe "Electron v4.0.0-beta.10"

Fiddle should probably default to whatever electron@latest is on npm :)

[felixrieseberg]

Fiddle should probably default to whatever electron@latest is on npm :)

Easier said than done, at least without introducing a decent amount of complexity. The list of Electron releases is downloaded on the fly and changing the default value after the fact would require using mutliple version states.

[erickzhao]

Could we fetch the latest version from the NPM version with the latest-version package (link) and attempt to set that version from the version list as the default?

I can see it working well for the purposes of the issue. However, I don't know if we want to add yet another dependency to Fiddle's package.json.

cc @felixrieseberg @nornagon