Use fiona.odict.OrderedDict instead of collections

OrderedDict was introduced in Python 2.7. Fiona uses the
ordereddict module for versions < 2.7. Use fiona.odict rather
than duplicating its effort

geopandas/io/file.py

@@ -1,7 +1,7 @@
-import collections
 import os
 
 import fiona
+from fiona.odict import OrderedDict
 import numpy as np
 from shapely.geometry import mapping
 
@@ -81,7 +81,7 @@ def convert_type(in_type):
             out_type = 'int'
         return out_type
 
-    properties = collections.OrderedDict([
+    properties = OrderedDict([
         (col, convert_type(_type)) for col, _type in
         zip(df.columns, df.dtypes) if col != 'geometry'
     ])

tests/test_geodataframe.py

@@ -1,6 +1,5 @@
 from __future__ import absolute_import
 
-import collections
 import json
 import os
 import tempfile
@@ -12,6 +11,7 @@
 from shapely.geometry import Point, Polygon
 
 import fiona
+from fiona.odict import OrderedDict
 from geopandas import GeoDataFrame, read_file, GeoSeries
 from .util import unittest, download_nybb, assert_geoseries_equal, connect, \
                   create_db, validate_boro_df, PANDAS_NEW_SQL_API
@@ -325,7 +325,7 @@ def test_to_file_schema(self):
         
         """
         tempfilename = os.path.join(self.tempdir, 'test.shp')
-        properties = collections.OrderedDict([
+        properties = OrderedDict([
             ('Shape_Leng', 'float:19.11'),
             ('BoroName', 'str:40'),
             ('BoroCode', 'int:10'),