Update GeneGCBatch.pm

Account for ncRNAs that have GC content 0 eg. C.elegans WBGene00197932.
Update GeneGC.pm

Account for ncRNAs that have GC content 0 eg. C.elegans WBGene00197932.
Merge pull request #9 from ima23/release/76

GeneGC, GeneGCBatch update to account for ncRNAs with GC 0