Add multiple tracker support GA events

[tarikhamilton]

Trackers now support an array or string and will fire an event to multiple trackers, if specified.

Checklist

• I have added tests that prove my fix is effective or that my feature works.
• I have added all necessary documentation (if appropriate)

What was done

I made trackers in Google Analytics events support arrays of named trackers. You will now be able to achieve this:

const eventsMap = {
  [LOCATION_CHANGE]: trackPageView(
    action => ({
      hitType: 'pageview',
      page: action.payload.pathname
    }),
    ['trackerOne', 'trackerTwo']
  )
};

Associated Issues

#289

[ttmarek]

@tarikhamilton absolutely fantastic!

These changes are available in @redux-beacon/google-analytics@1.1.0. Enjoy!