Initial work for running unit tests on minitest

This includes a significant number of changes to tests to root out order
dependencies, but probably hasn't caught them all.

It also doesn't appear to work right with Rails 3.0 in test:env yet, so that'll
be my bit of work to tackle on this.
RUBY-1253 Capture attr flags for TT and errors

Previously we had one master config value, "capture_attributes.traces" that
controlled both TT's and error collection of custom parameters. These are now
independently togglable.
test:env fixes for Rails 3+4 on MiniTest
Merge branch 'dev' into minitest_for_unit_tests
Removing debugging wrongly added to Gemfile
RUBY-1255 CHANGELOG entry for metric timestamps fix
Merge pull request #352 from newrelic/RUBY-1255-changelog

RUBY-1255 CHANGELOG entry for metric timestamps fix
Update Gemfiles and test helper for MiniTest

This changeset gets the `rake test:env` command working across the various
Ruby and Rails versions. We stop pulling in some test helper files and also
clean up how we're pulling in mocha now that we've moved solidly to a newer
version.
Removing unnecessary require that's creating warnings on REE
Merge pull request #348 from newrelic/RUBY-1253-error-and-tt-switches

RUBY-1253 Capture attribute flags for TT and errors
Merge remote-tracking branch 'origin/release' into dev
Fixing ordering dependency in test
Guard for MiniTest
RUBY-1253 Safer exception handling on RUM loader

If we had an exception during generating the JS for either the loader or config
we would fail the users request. Not cool.

We now trap and log if anything goes badly wrong in those cases. This is done
in the JavascriptInstrumentor rather than the middleware to make sure that
clients using manual instrumentation also get the protection.

The primary worry is JSON serialization failures from our NewRelic.json_dump
call.
Merge pull request #356 from newrelic/RUBY-1253-catch-exceptions

RUBY-1253 Safer exception handling on RUM loader
RUBY-1237 Skip DB query encoding handling test on rbx, due to an rbx bug

See https://github.com/rubinius/rubinius/issues/2899

We should also stop subclassing String for our Database::Statement class, but
that will likely have downstream fallout, especially for the serialization we do
to send data from Resque child processes to the master process.
Don't need to pin mocha version anymore
Merge branch 'minitest_for_unit_tests' into dev

Conflicts:
	test/environments/rails21/Gemfile
	test/environments/rails22/Gemfile
	test/environments/rails23/Gemfile
Merge pull request #355 from newrelic/RUBY-1237-rbx-skip

RUBY-1237 Skip DB query encoding handling test on rbx, due to an rbx bug
Restoring end