Added supercontig in the term name for caching
Implemented read_polypeptide method
Implemented write_polypeotide method
Added polypeptide cvterm for caching
Activated read and write polypeptide handler
Added check for existence of featureloc result row
Added reading of polypeptide for dicty gff3 reader
Added both read and write polypeptide handlers
Passing all cds to write_polypeptide method for completeness
If exists, get polypeptide coordinates from flanking cds
Remove .P suffix from ppolypeptide id of discoiduem
Merge pull request #142 from dictyBase/feature/export-polypeptide

Feature/export polypeptide