Tag generation tool for ATS-Postiats

As mentioned in
https://groups.google.com/forum/#!topic/ats-lang-users/q3yUCS_2YSk,
patsopt is now able to suport –taggen option as well. Please refer to
http://ats-documentation.readthedocs.org/en/latest/atstools/taggen/content.htmlfor the updated information of usage.