Timezones are not comparable between different pytz versions
I have HDF5 files created in 0.12 which were localized to a timezone ('US/Eastern').  When the dataframe is updated, it is done by calling combine_first which ultimately calls tseries.index.join.  Now when I try to update in 0.14, the HDF5 representation changes.  This is because of the different versions of pytz and timezone representation (see below), both sets of data will be converted to UTC and ultimately saved in UTC rather than US/Eastern.  This certainly surprised me.  This is using master branch as of this morning.

```
tz
Out[10]: <DstTzInfo 'US/Eastern' LMT-1 day, 19:04:00 STD> #New data
data.index.tz
Out[11]: <DstTzInfo 'US/Eastern' EST-1 day, 19:00:00 STD> #Saved data
data.index.tz == tz
Out[12]: False
```

Also, in ipython typing  "data.index.tz" gets stuck at "data.index." for about 20 seconds and my CPU spikes to 100% before completing.  I don't know if this is simply related to the versions or something else.
