Iso date timezone is not decoded in Series.read_json
#### Problem description

If I'm trying to load json data thought the Series.read_json considering the following command line :

```python
pd.read_json('{"2019-01-01T11:00:00.000Z":88.352985054,"2019-01-01T12:00:00.000Z":90.091719896,"2019-01-01T13:00:00.000Z":15}', typ='series', orient='index').index
```
I've go the following output 
```
DatetimeIndex(['2019-01-01 11:00:00',
               '2019-01-01 12:00:00', '2019-01-01 13:00:00'],
              dtype='datetime64[ns]', freq=None)
```

The timezone is contained in the 'Z' at the end of the timestamp string. It means that it's a UTC time. More information you can consult the wikipedia page for iso date https://fr.wikipedia.org/wiki/ISO_8601

#### Expected Output
UTC timezone should be mentionned :
```
DatetimeIndex(['2019-01-01 11:00:00',
               '2019-01-01 12:00:00', '2019-01-01 13:00:00'],
              dtype='datetime64[ns, UTC]', freq=None)
```

#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.7.final.0
python-bits: 64
OS: Linux
OS-release: 4.15.0-45-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: fr_FR.UTF-8
LOCALE: fr_FR.UTF-8

pandas: 0.24.1
pytest: None
pip: 19.0.3
setuptools: 40.6.2
Cython: None
numpy: 1.16.1
scipy: None
pyarrow: None
xarray: None
IPython: 7.2.0
sphinx: None
patsy: None
dateutil: 2.8.0
pytz: 2018.3
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 3.0.2
openpyxl: 2.6.0
xlrd: 1.2.0
xlwt: None
xlsxwriter: None
lxml.etree: None
bs4: 4.6.3
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None

[paste the output of ``pd.show_versions()`` here below this line]

</details>
