Add check for cert existence before binding
Add check for cert existence before binding

If a cert doesn't exist, it shouldn't try and bind it.
Display a better error message than netsh would give
Fixes #230

opscode-cookbooks/windows,modulexcite/windows,stuartpreston/windows,mrwizard82d1/windows,shoekstra/chef-windows,daptiv/windows,urban-institute/windows,rlaveycal/windows,jboeshart/windows,autoclone/windows,GannettDigital/chef-windows,protec-cookbooks/windows,juliandunn/windows,Chhed13/windows,chef-cookbooks/windows,blairham/windows-cookbook,wildbillcat-cookbooks/windows,criteo-forks/windows,tophercullen/windows,ruicovelo/windows