TimedeltaIndex + Timestamp -> no overflow error
When adding a TimedeltaIndex and a Timestamp this overflows instead of raising (pydata/xarray#975).

```
import pandas as pd

# overflow error (correct)
pd.to_timedelta(106580, 'D') + pd.Timestamp('2000')
# no overflow error (?)
pd.to_timedelta([106580], 'D') + pd.Timestamp('2000')
```
#### output of `pd.show_versions()`
## INSTALLED VERSIONS

commit: None
python: 2.7.12.final.0
python-bits: 64
OS: Linux
OS-release: 3.13.0-24-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.1
nose: None
pip: 8.1.2
setuptools: 25.1.6
Cython: None
numpy: 1.11.1
scipy: None
statsmodels: None
xarray: 0.7.2-73-g584e703
IPython: 5.1.0
sphinx: None
patsy: None
dateutil: 2.5.3
pytz: 2016.6.1
blosc: None
bottleneck: 1.1.0
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.8
boto: None
pandas_datareader: None

edit: 'D' as unit
