A PowerDNS pipe backend with the following features:
    
    - Uses gevent for Asynchrony.
    - Answers predefined DNS queries dynamically, based on result of http probes of given IP addresses.
    - Early tests show good results, for functionality and for performance.
    
How to use it:
    
    - Ensure Python library gevent is installed. 
    
    - python setup.py install
    
    - Edit /etc/pdns/pdns.conf as needed. Example:
        
    distributor-threads=1
    cache-ttl=20
    query-cache-ttl=0
    wildcards=no
    launch=pipe
    pipe-command=/usr/bin/pdns-glb.py
    pipe-timeout=500
    pipebackend-abi-version=2
    pipe-regex=^(www\.|other\.)?example\.com;(A|ANY)$
    
    - Copy pglb.conf to /etc/pdns, and edit as needed.