Direct users to discourse prior to filing issues. (#1525)
Direct users to discourse prior to filing issues. (#1525)

CONTRIBUTING.md instructs users to file Github issues for support
requests.

Modify the instructions to redirect users to Discourse.
denverwilliams/linkerd,linkerd/linkerd,linkerd/linkerd,BuoyantIO/linkerd,denverwilliams/linkerd,denverwilliams/linkerd,denverwilliams/linkerd,linkerd/linkerd,BuoyantIO/linkerd