create cache path if missing
create cache path if missing

Create the cache directory path is missing. The gff file will not be
generated if the directory is missing.

asherkhb/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,asherkhb/coge