to_csv execution unreliable in combination with for loop
I am outputting a single column from a dataframe to a csv. The data, however, is too long for some older downstream applications, so I have the csv add line breaks every `size` items so that individual rows in the output aren't too long.

#### Example
```python
from tkinter import Tk
from tkinter import filedialog
import pandas as pd
import numpy as np

Tk().withdraw() # we don't want a full GUI, so keep the root window from appearing
infilename = filedialog.askopenfilename()# show an "Open" dialog box and return the path to the selected file
data = pd.read_csv(infilename, header=None) #usecols=[0], only get 1st column, specify no header
outfilename = filedialog.asksaveasfile() #get save location

size=50 #number of items per line
col=0
indexes = np.arange(0,len(data),size)#have to use numpy since range is now an immutable type in python 3
indexes = np.append(indexes,[len(data)]) #add the uneven final index
for i in range(len(indexes)-1):
    holder = pd.DataFrame(data.iloc[indexes[i]:indexes[i+1],col]).T
    holder.to_csv(outfilename, index=False, header=False)
```

#### Expected Output
for input: 
A,B,C,D,E,F,G,H,I,J,K  #this is actually a column in the input, rendered horizontal for space

Becomes in the file (size=3):
A,B,C
D,E,F
G,H,I
J,K

Despite not throwing any errors, the final loop (with the uneven final index) does not write to the file, even though the information is assigned to `holder` without issue. Also, despite my not setting the `mode` param, acts as `w` and overwrites file if existing on the first loop, then acts as `a` and appends to the file on subsequent loops, indicating some possible statefullness which may be relevant. Since no errors are thrown, I cannot figure out why the final information is not being written. 

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

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 42 Stepping 7, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None

pandas: 0.18.1
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: 4.2.0
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>
