BUG: Different timezones for DatetimeIndex versus elements of DatetimeIndex
Huge fan of Pandas.  Thanks for all the hard work!

I've noticed an inconsistency.  The following `DatetimeIndex` object reports a different timezone compared to its elements:

``` python
In [1]: import pandas as pd

In [2]: idx = pd.date_range("2015-01-01", "2015-01-03", freq="D", tz="US/Eastern")

In [3]: idx.tz
Out[3]: <DstTzInfo 'US/Eastern' LMT-1 day, 19:04:00 STD>

In [4]: [timestamp.tz for timestamp in idx]
Out[4]: 
[<DstTzInfo 'US/Eastern' EST-1 day, 19:00:00 STD>,
 <DstTzInfo 'US/Eastern' EST-1 day, 19:00:00 STD>,
 <DstTzInfo 'US/Eastern' EST-1 day, 19:00:00 STD>]

In [6]: idx[0].tz == idx.tz
Out[6]: False
```

And here are my installed versions:

``` python
In [5]: pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.8.final.0
python-bits: 64
OS: Linux
OS-release: 3.16.0-37-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_GB.UTF-8

pandas: 0.16.1
nose: 1.3.4
Cython: 0.21.2
numpy: 1.9.2
scipy: 0.15.1
statsmodels: None
IPython: 3.1.0
sphinx: 1.2.3
patsy: None
dateutil: 2.4.2
pytz: 2015.2
bottleneck: 0.6.0
tables: 3.1.1
numexpr: 2.4
matplotlib: 1.4.3
openpyxl: 1.8.6
xlrd: 0.9.2
xlwt: 0.7.5
xlsxwriter: None
lxml: 3.3.6
bs4: None
html5lib: 0.999
httplib2: 0.9
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: 2.5.3 (dt dec mx pq3 ext)
```
