package: update loopback* to ~2.0.0-beta
package: update loopback* to ~2.0.0-beta

Replace github dependencies with npm dependencies.

Add `~` to version specifiers to support future beta releases.

uniconstructor/loopback-example-offline-sync,jeffcressman/loopback-example-offline-sync-react,jouke/loopback-connector-cordova-sqlite,uniconstructor/loopback-example-offline-sync,jeffcressman/loopback-example-offline-sync-react