Adjust logging level for `tracing` crate

[Matt Tanous]

A number of the functions in this library are instrumented with tracing::instrument, but that defaults to an INFO logging level. It would be helpful to set these to something higher like DEBUG so we can manage whether these low level methods will show up in the logs when we instrument our own applications.

[Dirkjan Ochtman]

Sure, would you be able to submit a PR with specific suggestions?

[Matt Tanous]

@djc Sure thing, I have opened #101 to adjust these log levels. Thanks!