updates pandas version to latest version that passes unit tests

Author: alixhami

bigquery/setup.py

@@ -59,7 +59,7 @@
 ]
 
 EXTRAS_REQUIREMENTS = {
-    'pandas': ['pandas >= 0.3.0'],
+    'pandas': ['pandas >= 0.17.1'],
 }
 
 setup(

bigquery/tests/system.py

@@ -1448,6 +1448,7 @@ def test_create_table_rows_fetch_nested_schema(self):
     def _fetch_dataframe(self, query):
         return Config.CLIENT.query(query).result().to_dataframe()
 
+    @unittest.skipIf(pandas is None, 'Requires `pandas`')
     def test_nested_table_to_dataframe(self):
         SF = bigquery.SchemaField
         schema = [