Update README.md

Update __init__.py

fix a bug. use sys.version_info.major can't be used in Python2.5

tag version 0.29.1

tag version 0.29

tag version 0.28.4

tag version 0.28.3

tag version 0.28.1; fix bug of file leak

tag version 0.28; lazy load

tag version 0.27; parallel mode