updated yajl-ruby

NewRelic thread profiler did not work with older yajl-ruby as it was causing segfaults

Signed-off-by: Dmitriy Kalinin <dmitriy@pivotallabs.com>
Bump vendor/errors for https://github.com/cloudfoundry/errors/pull/12

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>