Build Refactoring

[jshcrowthe]

Issues

There are several issues with the build process that I'd like to address:

• The current build process ignores Typescript compile errors, allowing invalid TS (that fails at release time) to get into the master of the SDK. This is WAI from a typescript viewpoint, so I'm addressing this in some refactoring I've been looking at for a while.
• The current build process is quite slow
• The current build process doesn't lend itself to highly optimized use cases

Change Summary

The changes are broken down as follows:

@firebase/* Packages (not including the types packages)

• Removed gulpfile.js and associated gulp dependencies
• Added rollup.config.js and associated rollup dependencies (including rollup-plugin-typescript2 which fails builds for TS errors)
• Updated the main, module, browser fields of each package.json to conform to rollup standards
• Updated the "scripts" for each package that were referencing gulp to now reference rollup (as pertinent)

@firebase/*-types Packages

• Removed unused test files and associated test setup

Results

Build Time

Before PR: 130.11s
After PR: 78.30s

Build Size

Before PR

Asset	Size
firebase-app.js	35.1 kB
firebase-auth.js	145 kB
firebase-database.js	178 kB
firebase-firestore.js	280 kB
firebase-functions.js	5.85 kB
firebase-messaging.js	26.5 kB
firebase-storage.js	33.7 kB

After PR

Asset	Size
firebase-app.js	13 kB
firebase-auth.js	141 kB
firebase-database.js	178 kB
firebase-firestore.js	302 kB
firebase-functions.js	6.8 kB
firebase-messaging.js	33 kB
firebase-storage.js	31 kB

[mmermerkaya]

Should these be "yarn build"?

[jshcrowthe]

If we were leveraging yarn as a devDependency here, yes. But since we can't assume yarn exists, sticking w/ NPM is functionally equivalent, and is safer.