add analytics class to training

[spgandhi]

Proposal - create a separate class for analytics that would be accessible via the GraphAcademyPage class.

Constraints

1. We only want to start tracking after the user is logged in

Platforms to integrate

1. Mixpanel
2. Intercom

Functions -

1. init() - initates the tracking libraries and sets identify eg: mixpanel.indentity(user_id);
2. track(eventName, meta, platform) - platform will specify which platform to send data to. For eg, we might have a event that we want to track in Mixpanel but not in Intercom.

Sandbox Implementation:

.....
shouldTrackPlatform(options, platformName) {
	return !!(
		!options
		|| (!options.all && options[platformName])
		|| (options.all && options[platformName] !== false)
	);
}

track(eventName, meta, platform = null) {
         const shouldTrackMixPanel = this.shouldTrackPlatform(platform, 'mixpanel');
         const shouldTrackIntercom = this.shouldTrackPlatform(platform, 'intercom');

        if(shouldTrackMixpanel) ..............
        if(shouldTrackIntercom) ..............
}
.....

Possible platform values

1. {all: false, mixpanel: true} - tracks only in mixpanel
2. {all: true, mixpanel: false} - track everything but mixpanel

Inspired by segment.com implementation - https://segment.com/docs/connections/sources/catalog/libraries/website/javascript/#selecting-destinations