make trackEvent take any metadata, fixes #77

[wbhob]

Summary of changes:

Intended/example use case:

Checklist:

• [ ] npm run build runs without error
• [ ] ng serve spawns app, Intercom messenger is visible and interactive, and there are no errors in the console

Closes issue: #

[scott-wyatt]

This should be fine to merge. If you update the package.json and ng-package.json version numbers, this can be released by circle ci when a release v tag release is made here on github.