Update placeholderRegexp to support parens
Update placeholderRegexp to support parens

And only replace values that would be invalid YAML, meaning the
{{old_placeholder}} style.

mcb/pcf-pipelines,sandyg1/pcf-pipelines,pivotal-cf/pcf-pipelines,cah-josephgeorge/pcf-pipelines,BrianMMcClain/pcf-pipelines,pvsone/pcf-pipelines,sandyg1/pcf-pipelines,pivotal-cf/pcf-pipelines,pivotal-cf/pcf-pipelines,BrianMMcClain/pcf-pipelines,rahulkj/pcf-pipelines,sandyg1/pcf-pipelines,pvsone/pcf-pipelines,cah-josephgeorge/pcf-pipelines,rahulkj/pcf-pipelines,cah-josephgeorge/pcf-pipelines,pvsone/pcf-pipelines,mcb/pcf-pipelines,rahulkj/pcf-pipelines,pivotal-cf/pcf-pipelines,mcb/pcf-pipelines,rahulkj/pcf-pipelines,sandyg1/pcf-pipelines