pd.to_timedelta now raise an OverflowError when plot time series data using matplotlib
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from matplotlib import dates

t = np.arange(10)
ts = pd.datetime(2017, 11, 16) + pd.to_timedelta(t, 's')
df = pd.DataFrame(t, index=ts)

fig, ax = plt.subplots()
ax.plot(df)
# workaround:
# ax.plot(df.index.to_pydatetime(), df)

# format time axis
hfmt = dates.DateFormatter('%m/%d %H:%M')
ax.xaxis.set_major_formatter(hfmt)
fig.autofmt_xdate()
plt.show()
```
#### Problem description

Version: `pandas-0.21.0`

trace:
```
Traceback (most recent call last):

  File "D:\Anaconda3\lib\site-packages\IPython\core\formatters.py", line 332, in __call__
    return printer(obj)

  File "D:\Anaconda3\lib\site-packages\IPython\core\pylabtools.py", line 237, in <lambda>
    png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))

  File "D:\Anaconda3\lib\site-packages\IPython\core\pylabtools.py", line 121, in print_figure
    fig.canvas.print_figure(bytes_io, **kw)

  File "D:\Anaconda3\lib\site-packages\matplotlib\backend_bases.py", line 2208, in print_figure
    **kwargs)

  File "D:\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 507, in print_png
    FigureCanvasAgg.draw(self)

  File "D:\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 430, in draw
    self.figure.draw(self.renderer)

  File "D:\Anaconda3\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)

  File "D:\Anaconda3\lib\site-packages\matplotlib\figure.py", line 1295, in draw
    renderer, self, artists, self.suppressComposite)

  File "D:\Anaconda3\lib\site-packages\matplotlib\image.py", line 138, in _draw_list_compositing_images
    a.draw(renderer)

  File "D:\Anaconda3\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)

  File "D:\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2399, in draw
    mimage._draw_list_compositing_images(renderer, self, artists)

  File "D:\Anaconda3\lib\site-packages\matplotlib\image.py", line 138, in _draw_list_compositing_images
    a.draw(renderer)

  File "D:\Anaconda3\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)

  File "D:\Anaconda3\lib\site-packages\matplotlib\axis.py", line 1133, in draw
    ticks_to_draw = self._update_ticks(renderer)

  File "D:\Anaconda3\lib\site-packages\matplotlib\axis.py", line 974, in _update_ticks
    tick_tups = list(self.iter_ticks())

  File "D:\Anaconda3\lib\site-packages\matplotlib\axis.py", line 921, in iter_ticks
    for i, val in enumerate(majorLocs)]

  File "D:\Anaconda3\lib\site-packages\matplotlib\axis.py", line 921, in <listcomp>
    for i, val in enumerate(majorLocs)]

  File "D:\Anaconda3\lib\site-packages\matplotlib\dates.py", line 538, in __call__
    dt = num2date(x, self.tz)

  File "D:\Anaconda3\lib\site-packages\matplotlib\dates.py", line 441, in num2date
    return _from_ordinalf(x, tz)

  File "D:\Anaconda3\lib\site-packages\matplotlib\dates.py", line 256, in _from_ordinalf
    dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)

OverflowError: Python int too large to convert to C long

<matplotlib.figure.Figure at 0xebecc88>
```

#### Expected Output

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

```
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.3.final.0
python-bits: 64
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: en
LOCALE: None.None

pandas: 0.21.0
pytest: 3.2.1
pip: 9.0.1
setuptools: 36.5.0.post20170921
Cython: 0.26.1
numpy: 1.13.3
scipy: 1.0.0
pyarrow: None
xarray: 0.9.6
IPython: 6.1.0
sphinx: 1.6.3
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.2
feather: None
matplotlib: 2.1.0
openpyxl: 2.4.8
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.2
lxml: 4.1.0
bs4: 4.6.0
html5lib: 0.999999999
sqlalchemy: 1.1.13
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
```

#### workarounds

using 
```python
ax.plot(df.index.to_pydatetime(), df)
```
instead
```python
ax.plot(df)
```

This problem does not occur prior to `0.21.0`