Upload of artifacts should be retried on failure

[timfish]

On my CI server, sometimes uploading of artifacts to Github fails. Uploading should be re-attempted a few times.

Publishing to Github (owner: CompanyName, project: AppName, version: 1.0.1-beta)
Uploading appname-1.0.1-beta.dmg to GitHub
Uploading appname-1.0.1-beta-mac.zip to GitHub
Uploading latest-mac.json to GitHub
Uploading latest-mac.yml to GitHub
Error: write EPIPE
    at exports._errnoException (util.js:1050:11)
    at WriteWrap.afterWrite (net.js:814:14)
From previous event:
    at CancellationToken.createPromise (/Users/vagrant/git/node_modules/electron-builder-http/src/CancellationToken.ts:51:5)
    at NodeHttpExecutor.doApiRequest (/Users/vagrant/git/node_modules/electron-builder-util/src/nodeHttpExecutor.ts:51:30)
    at /Users/vagrant/git/node_modules/electron-publish/src/gitHubPublisher.ts:107:35
    at Generator.next (<anonymous>)
    at runCallback (timers.js:672:20)
    at tryOnImmediate (timers.js:645:5)
    at processImmediate [as _immediateCallback] (timers.js:617:5)
From previous event:
    at GitHubPublisher.doUpload (/Users/vagrant/git/node_modules/electron-publish/out/gitHubPublisher.js:163:11)
    at /Users/vagrant/git/node_modules/electron-publish/src/publisher.ts:74:16
    at Generator.next (<anonymous>)
    at /Users/vagrant/git/node_modules/graceful-fs/polyfills.js:287:18
    at FSReqWrap.oncomplete (fs.js:114:15)