BUG: Bug in csv parsing when passing dtype and names and the parsed data is a different data type (GH8833)
closes #8833 

```
In [5]: data = """1.0,a
   ...: nan,b
   ...: 3.0,c
   ...: """

In [8]: read_csv(StringIO(data),sep=',',names=['A','B'])
Out[8]: 
    A  B
0   1  a
1 NaN  b
2   3  c

In [9]: read_csv(StringIO(data),sep=',',names=['A','B'],dtype={'A' : int})
ValueError: cannot safely convert passed user dtype of <i8 for float64 dtyped data in column 0
```
