cell_to_csv for double quote escaping changed all tr to gsub
cell_to_csv for double quote escaping changed all tr to gsub

tr is not escaping double quote characters correctly, replaced with call to gsub.
xchanging-mm4/roo,fabien-michel/roo,roo-rb/roo,thotmx/roo,reshleman/roo,visagio/roo,maruware/roo,RobertRehberg/roo,stevendaniels/roo,pabloh/roo