print df.ix[..,..] changes dataframe?
These two codeblocks result in different dataframes:

``` python
import pandas as pd
import numpy as np
cont = ['one', 'two','three', 'four', 'five', 'six', 'seven']
dfb = pd.DataFrame({'a' : cont, "b":cont[3:]+cont[:3] ,'c' : np.arange(7)})
#print dfb.ix[0,"c"]
dfb.ix[7,'c'] = 1
print dfb
print dfb.ix[7,"c"]
print dfb.ix[0,"c"]

       a      b  c
0    one   four  0
1    two   five  1
2  three    six  2
3   four  seven  3
4   five    one  4
5    six    two  5
6  seven  three  6
7    NaN    NaN  1
1.0
0.0
```

and 

``` python
import pandas as pd
import numpy as np
cont = ['one', 'two','three', 'four', 'five', 'six', 'seven']
dfb = pd.DataFrame({'a' : cont, "b":cont[3:]+cont[:3] ,'c' : np.arange(7)})
print dfb.ix[0,"c"]
dfb.ix[7,'c'] = 1
print dfb
print dfb.ix[7,"c"]
print dfb.ix[0,"c"]

0
       a      b   c
0    one   four   0
1    two   five   1
2  three    six   2
3   four  seven   3
4   five    one   4
5    six    two   5
6  seven  three   6
7    NaN    NaN NaN
nan
0.0
```

pd.**version** = '0.12.0-922-gac1609e'

In the first case I also don't understand why the last column is changed to a float when I set an int.
