Bind messaging

[jamesdaniels]

Checklist

• Issue number for this PR: Messaging: TypeError: this.onTokenRefreshInternal is not a function #1855
• Docs included?: (yes/no; required for all API/functional changes)
• Test units included?: (yes/no; required)
• In a clean directory, yarn install, yarn test run successfully? (yes/no; required)

Description

• Changelogs and version bumps
• .bind() the messaging callbacks
• Another bug! onTokenRefresh doesn't actually return the token, just fires when you need to get it

Code sample

[jamesdaniels]

Available here for testing @angular/fire 5.0.2.

[jamesdaniels]

FYI @codediodeio

[davideast]

LGTM!