Fixed ncbi timeout

[mmzdouc]

Fixed NCBI timeout functionality by using concurrent.futures.
Previous requests-based implementation was blocked by the NCBI servers.
For future reference, here the error message:

urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='eutils.ncbi.nlm.nih.gov', port=443): Max retries exceeded with url: /entrez/eutils/efetch.fcgi?db=protein&id=BED42923.1&rettype=fasta&retmode=text (Caused by NewConnectionError("HTTPSConnection(host='eutils.ncbi.nlm.nih.gov', port=443): Failed to establish a new connection: [Errno 101] Network is unreachable"))