issue #48: fix a couple issues with dtrace support

- before this, if there were no non-raw streams on the logger the
  `str` for the dtrace probe.fire would not be created
- ensure that with no non-raw streams we only render a record's
  JSON string if the dtrace probe is enabled
issue #48: make dtrace-provider presence optional (disabled dtrace probes)

dtrace-provider is still in *dependencies* to strongly encourage
installing it. However I want bunyan.js to be useable for basic
usage standalone.
issue #48: changelog, add Bryan to AUTHORS, basic dtrace test suite

The test suite for this is a bit finnicky because root rights are
required to run dtrace. By default we run the dtrace.test.js file
with 'sudo'. Use this to skip the dtrace tests:
    SKIP_DTRACE=1 make test

Note taht 'make test09' is busted because dtrace-provider seems
busted with node 0.9.1 at least.
semi-reliable test case for dtrace support
more reliable dtrace test, drop node0.9 testing (dtrace-provider doesn't work)
prepare for 0.15.0 release
prep for future dev
better pitch for the dtrace support
'bunyan -p PID' support
prepare for 0.16.0 release
prep for future dev
ensure termination of child dtrace on CLI term by a signal
prepare for 0.16.1 release
prep for future dev
ensure dtrace stderr is piped through
prepare for 0.16.2 release
prep for future dev
back to dtrace-provider dep
prepare for 0.16.3 release
prep for future dev