docs: Update README.md for mixpanel (#253)
docs: Update README.md for mixpanel (#253)

* Update README.md for mixpanel

* Update README.md for mixpanel

* Update README.md for mixpanel: minor wording error

* Update README.md for mixpanel: improve the guide

* Update README.md for mixpanel: improved the guide

angulartics/angulartics2,angulartics/angulartics2,angulartics/angulartics2