global: pep8 and pep257 improvements

* Improves code style. (closes #6)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
tests: py.test with coverage and pep8 support

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
global: support for Python 3

* Fixes problems with exceptions handling and str/unicode.  (closes #7)
test: support for tox

* Adds support for tox testing.  (closes #4)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
README: Python 3 note removal

* Adds classifiers for Python versions 2.6, 2.7, and 3.3.

Reported-by: Tibor Simko <tibor.simko@cern.ch>
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Merge pull request #14 from jirikuncar/pep8

global: pep8 and pep257 improvements