TODOs for SNSAPI No.19: Find a simpler implementation for str2utc() and ...

...utc2str()

I found a new Python module 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 use "times" to replace the "datetime" and "dateutil" module to make a simpler implementation for str2utc() and utc2str()