A simpler implementation for str2utc() and utc2str()

I found a python library called "Times"(https://github.com/nvie/times)
"Times is a small, minimalistic, Python library for dealing with time conversions between universal time and arbitrary timezones."(https://pypi.python.org/pypi/times)
So I wrote a simpler new version of the str2utc() and utc2str()