Remind people about the mixer specific steps (#684)
Remind people about the mixer specific steps (#684)

* Remind people about the mixer specific steps

link to dev guide from contributing.md

* mixer -> Mixer per review comment

* opsa... one more

* changing per request

though using "foo-specific" vs "foo specific" isn't so clear (but english isn't my first language so...)

istio/old_mixer_repo,douglas-reid/mixer,ZackButcher/mixer,jmuk/mixer,guptasu/mixer,jmuk/mixer,guptasu/mixer,rkpagadala/mixer,rkpagadala/mixer,istio/old_mixer_repo,xiaolanz/mixer,xiaolanz/mixer,xiaolanz/mixer,rkpagadala/mixer,jmuk/mixer,guptasu/mixer,douglas-reid/mixer,ZackButcher/mixer,istio/old_mixer_repo,ZackButcher/mixer,douglas-reid/mixer