str.find returns dtype: float64
str.find fails to return integers

As per the docs it should return Series/Index of integer values


#### Code Sample, a copy-pastable example if possible

```
df[:5]
	0	1
0	ZAR12015	FastEthernet2/0/38
1	AFA12286	FastEthernet4/0/22
2	CAA12029	FastEthernet2/0/35
3	IFAA2302 	FastEthernet4/0/14
4	HFQ12009	FastEthernet5/38

df.loc[:,"1"].str.find("Ether")


6982    4.0
6983    4.0
6984    4.0
Name: 1, dtype: float64

df.loc[:,"1"].apply( lambda x : x[x.find("Ether"):])

AttributeError                            Traceback (most recent call last)
<ipython-input-39-73570bc63928> in <module>()
----> 1 df.loc[:,"1"].apply( lambda x : x[x.find("Ether"):])

C:\Users\X91437\Documents\Program Files\Anaconda\lib\site-packages\pandas\core\series.py in apply(self, func, convert_dtype, args, **kwds)
   2290             else:
   2291                 values = self.asobject
-> 2292                 mapped = lib.map_infer(values, f, convert=convert_dtype)
   2293 
   2294         if len(mapped) and isinstance(mapped[0], Series):

pandas\src\inference.pyx in pandas.lib.map_infer (pandas\lib.c:66116)()

<ipython-input-39-73570bc63928> in <lambda>(x)
----> 1 df.loc[:,"1"].apply( lambda x : x[x.find("Ether"):])

AttributeError: 'float' object has no attribute 'find'
```
# Your code here
```
#### Expected Output
6982    4
6983    4
6984    4

Name: 1, dtype: int 
```
#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 61 Stepping 4, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.19.1
nose: 1.3.7
pip: 8.1.2
setuptools: 23.0.0
Cython: 0.24
numpy: 1.11.1
scipy: 0.17.1
statsmodels: 0.6.1
xarray: None
IPython: 5.2.1
sphinx: 1.3.1
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.4
blosc: None
bottleneck: 1.1.0
tables: 3.2.2
numexpr: 2.6.0
matplotlib: 1.5.1
openpyxl: 2.3.2
xlrd: 1.0.0
xlwt: 1.1.2
xlsxwriter: 0.9.2
lxml: 3.6.0
bs4: 4.4.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.13
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.40.0
pandas_datareader: None

</details>
