start implement zipped nexson export for studies
start from non-zipped nexson exporter
zipfile works, but transfer closes prematurely
checkpoint before trying to get rid of the temporary file
Changed export_gzipNexon so that gzipFile creation uses a StringIO and avoids making any tempdirectories that couldn't be cleaned up.
Merge pull request #44 from OpenTreeOfLife/tm_issue22

export_gzipNexSON exporter