appId: String for identifying your app, if you use same Application Insights for multiple apps.
instrumentationKey, connectionString: Credentials for sending to Application Insights. connectionString is preferred for newer accounts and must contain both InstrumentationKey and IngestionEndpoint.
autoTrackPageVisitTime: Submits how long time a user spent on the previous page (see website for more information).
If jsonlite is playing tricks on the arguments given, wrap the value with I. E.g. if you want to force an atomic vector of length 1 to be parsed as an array, use I(3.14).