CLN: Rename module, backward compat

Rename FX to fx
Remove use of Int64Index which was added in 0.20

Author: bashtage

pandas_datareader/yahoo/daily.py

@@ -5,7 +5,6 @@
 from pandas import (DataFrame, to_datetime, concat)
 from pandas_datareader.base import _DailyBaseReader
 from pandas_datareader._utils import (RemoteDataError, SymbolWarning)
-from pandas.core.indexes.numeric import Int64Index
 import pandas.compat as compat
 
 
@@ -114,7 +113,7 @@ def read(self):
                 dfs = self._dl_mult_symbols(self.symbols)
 
             for k in dfs:
-                if isinstance(dfs[k].index, Int64Index):
+                if 'Date' in dfs[k]:
                     dfs[k] = dfs[k].set_index('Date')
                 dfs[k] = dfs[k].sort_index().dropna(how='all')
 

pandas_datareader/yahoo/FX.py renamed to pandas_datareader/yahoo/fx.py

@@ -5,7 +5,6 @@
 from pandas_datareader.yahoo.daily import YahooDailyReader
 import pandas.compat as compat
 from pandas_datareader._utils import (RemoteDataError, SymbolWarning)
-from pandas.core.indexes.numeric import Int64Index
 
 
 class YahooFXReader(YahooDailyReader):
@@ -65,7 +64,7 @@ def read(self):
             else:
                 df = self._dl_mult_symbols(self.symbols)
 
-            if isinstance(df.index, Int64Index):
+            if 'Date' in df:
                 df = df.set_index('Date')
 
             if 'Volume' in df: