Allow using multiple pageTrackers and eventTrackers

Conflicts:
	dist/angulartics-ga.min.js
	dist/angulartics-mixpanel.min.js
	dist/angulartics.min.js
build dist
Support for multiple GA trackers; ref https://github.com/luisfarzati/angulartics/issues/129

Conflicts:
	dist/angulartics-ga.min.js
build dist