pd.Timestamp.today() / pd.to_datetime('today') returns date with time information
Calling **pd.Timestamp.today()** or **pd.to_datetime('today')** returns both the date and time information. This is unexpected behavior since the time information should be returned with **.now()** or **'now'**, respectively, while the **.today()** and **'today'** should trim to simply the date information.

Example code:

```python
import pandas as pd
print(pd.Timestamp.today())
print(pd.to_datetime('today'))
```

#### Expected Output

pd.Timestamp('2018-09-14 00:00:00')

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

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.7.0.final.0
python-bits: 64
byteorder: little
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.23.4
pytest: None
pip: 18.0
setuptools: 39.0.1
Cython: 0.28.5
numpy: 1.15.1
scipy: 1.1.0
pyarrow: None
xarray: None
IPython: 6.5.0
sphinx: None
patsy: None
dateutil: 2.7.3
pytz: 2018.5
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.2.3
openpyxl: 2.5.4
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.5
lxml: None
bs4: None
html5lib: 1.0.1
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
</details>
