trackTrace API does not support setting severity level

[GFoley83]

The API for trackTrace:
https://github.com/MarkPieszak/angular-application-insights/blob/master/src/app-insight.service.ts#L145

needs to be extended to support setting the severity level e.g. info, warn, etc.

As can be seen here:

https://github.com/Microsoft/ApplicationInsights-JS/blob/master/API-reference.md#tracktrace

[MarkPieszak]

Fixed via
55a453c

Thanks for finding this one! 👍 💯

[GFoley83]

Cheers for the quick turnaround @MarkPieszak. Is there any chance of getting this for version 4 as well?