Normalize all references to the utils module

This change fixes a bug in the logger module introduced by #171, which
imported the utils module as `utils` but referenced it later as `util`.

As well, all references to the old `util` in source, tests, and docs are
normalized to `utils`.
Merge pull request #173 from flightjs/fix/util

Normalize all references to the utils module
Merge remote-tracking branch 'origin/master' into no_reidentify