Change Travis build status URL.
Adds Python3 compatibility, using `six` module.
Also, Travis config was added, to run tests against python 2.7 and 3.2.
Update the README.
No need to explain all the details in the README.
It is enough (and way simpler) for users to only know the to_universal()
Remove the ambiguous function from_universal.
Since we support UNIX timestamps, too, now, it is unclear what will be
the result of the call. Use to_local() explicitly instead.
Fix wording: "absolute" -> "universal".
Support auto-detection of UNIX timestamps in to_universal().
Fixup the last note in the README.
Add a note on using `to_local()`.
Write more documentation in the README.
Add some README paragraphs.