Finally! Full support for Angular 2-8

See https://single-spa.js.org/docs/ecosystem-angular.html for full documentation. See release notes for beta and rc versions of 3.0.0 for all changes.

Changes from 3.0.0-rc.1

• Remove errant peerDependency in Angular 7. (7ab71e4, #79
• Switching to prepublishOnly script (3bd9359)