search path of pandas read_csv function
Hi 
read_csv funciton of pandas is able to read csv file in local folder, but it is not able to read the csv file in folder added by sys.path.append function.

Please check my test code:
data_1001_0001.csv file locates in C:\doc\datasets which is added by command sys.path.append

```python

import pandas as pd
import sys
sys.path.append(r'C:\doc\datasets')
# data_1001_0001.csv file locates in C:\doc\datasets 
df = pd.read_csv('data_1001_0001.csv')

```

Error is:
IOError: File data_1001_0001.csv does not exist
