Use tz.gettz() instead of zoneinfo.gettz()
zoneinfo.gettz() seems to have problems (1 & 2) on system which do not install
the zoninfo tarball (e.g. Debian, Gentoo and Fedora) but rely on the system
zoneinfo files. This results in test failures (3 & 4)
tz.gettz() doesn't suffer from this problem.

1 https://github.com/dateutil/dateutil/issues/8
2 https://github.com/dateutil/dateutil/issues/11
closes https://github.com/pydata/pandas/issues/9059
closes https://github.com/pydata/pandas/issues/8639
closes #10121

Signed-off-by: Justin Lecher jlec@gentoo.org

the is an api issue for dateutil

the current settings work on all platforms 
except yours

pandas should not be fixing the problem rather dateutil should
 @jlec so this completely breaks windows. That is the reason I changed it in the first place. That said if you wanted to put in different imports (e.g. use the current code if on windows, else use what you did). I think that would be acceptable, until dateutil actually fixes this.

lmk
 @jlec any interest in doing the change I propose above?
 @jreback I didn't saw your direct reply. I will look into this this week.
 @jreback which way do you prefer to check for windows, os.name or sys.platform?
 use sys.platform != 'win32'
 Sorry for the long delay. Somehow I don't get mails from GH correctly
 @jlec can you update?
 @jlec you need to rebase on master, see howtos in [here](http://pandas-docs.github.io/pandas-docs-travis/contributing.html)
 It's not the wrong rebase, I have a merge commit. I will try to clean that up.
 ok, pls add a release note in v0.17.0.txt mentioned all the above issues (you can just list them with a single note). and squash to a single commit.
 Hopefully everything is now respecting the contribution guidelines. If not, please tell me what needs to be fixed.
 ok, ping me when travis is green and I will merge.
 @jlec thanks.
