Make CI test python 2 and 3 (#48)

- Add python 3.6 to .travis.yml
- Fix file open warnings in tests for python3

Author: bchew

.travis.yml

@@ -3,6 +3,7 @@ env:
   - BOTO_CONFIG=/dev/null
 python:
   - "2.7"
+  - "3.6"
 before_install:
   # install and run latest DynamoDB Local
   - mkdir /tmp/dynamodb_local

test/test.py

@@ -11,10 +11,21 @@
 class TestDynamoDump(unittest.TestCase):
 
     def setUp(self):
-        self.test_table_schema = json.load(open(TEST_DATA_PATH + "/" + SCHEMA_FILE))
-        self.restored_test_table_schema = json.load(open(DUMP_DATA_PATH + "/" + SCHEMA_FILE))
-        self.test_table_data = json.load(open(TEST_DATA_PATH + "/data/" + DATA_FILE))
-        self.restored_test_table_data = json.load(open(DUMP_DATA_PATH + "/data/" + DATA_FILE))
+        with open(TEST_DATA_PATH + "/" + SCHEMA_FILE, 'r') as f:
+            data = f.read()
+        self.test_table_schema = json.loads(data)
+
+        with open(DUMP_DATA_PATH + "/" + SCHEMA_FILE, 'r') as f:
+            data = f.read()
+        self.restored_test_table_schema = json.loads(data)
+
+        with open(TEST_DATA_PATH + "/data/" + DATA_FILE, 'r') as f:
+            data = f.read()
+        self.test_table_data = json.loads(data)
+
+        with open(DUMP_DATA_PATH + "/data/" + DATA_FILE, 'r') as f:
+            data = f.read()
+        self.restored_test_table_data = json.loads(data)
 
     def test_schema(self):
         self.assertEqual(self.test_table_schema["Table"]["AttributeDefinitions"],