Amend `lp.fs.log` and `lp.fs.time` to include `lp.fs.now`

Implement `lp.fs.now` to return `epoch`

#### Notes
`window.performance.now()` is relative to the `startNavigation` performance value. Therefore, more calculations are required on the client to get the event timestamp. Using `Date.now()` or `new Date().getTime()` is faster and requires no calculation on the client.

We want to assign the `t` attribute (a Timestamp) to each event pushed to the buffer, and not just in `fs.time`