Find solution to allow starting to trace from any point in time

[christophebedard]

As mentioned in #40 (and in the README), we need to start tracing before the application launches to collect initialization information/metadata.

We current workaround is to start tracing before the application launches, then stop after 30-60 s, and then later on (when needed) start tracing again. This still requires us to actually set up tracing before the application launches.

1. Store the metadata and re-emit it at regular intervals. Then we'd simply need to record one metadata "burst."
2. Store init metadata and "state dump" it when we start tracing like LTTng does for its own stuff