MAINT: Use explicit syntax for relative imports.

Python 3 requires using dot syntax for relative imports,
otherwise the import is treated as an absolute import, i.e.
an import of a module from outside of the project.

By using dot syntax now, imports should be compatible with both
Python 2.7 and Python 3.

zipline/__init__.py

@@ -6,10 +6,10 @@ Zipline
 # it is a place to expose the public interfaces.
 
 
-import data
-import finance
-import gens
-import utils
+from . import data
+from . import finance
+from . import gens
+from . import utils
 
 from algorithm import TradingAlgorithm
 

zipline/data/__init__.py

@@ -1,3 +1,3 @@
-import loader
+from . import loader
 
 __all__ = ['loader']

zipline/data/benchmarks.py

@@ -22,7 +22,7 @@ from functools import partial
 
 import requests
 
-from loader_utils import (
+from . loader_utils import (
     date_conversion,
     source_to_records,
     Mapping

zipline/data/loader.py

@@ -22,7 +22,7 @@ from datetime import timedelta
 
 import logbook
 
-from treasuries import get_treasury_data
+from . treasuries import get_treasury_data
 import benchmarks
 from benchmarks import get_benchmark_returns
 

zipline/data/treasuries.py

@@ -19,7 +19,7 @@ import requests
 from collections import OrderedDict
 import xml.etree.ElementTree as ET
 
-from loader_utils import (
+from . loader_utils import (
     guarded_conversion,
     safe_int,
     Mapping,

zipline/protocol.py

@@ -15,7 +15,7 @@
 from collections import defaultdict
 import datetime
 
-from utils.protocol_utils import Enum
+from . utils.protocol_utils import Enum
 
 # Datasource type should completely determine the other fields of a
 # message with its type.

zipline/transforms/__init__.py

@@ -13,11 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from mavg import MovingAverage
-from stddev import MovingStandardDev
-from vwap import MovingVWAP
-from returns import Returns
-from utils import BatchTransform, batch_transform
+from . mavg import MovingAverage
+from . stddev import MovingStandardDev
+from . vwap import MovingVWAP
+from . returns import Returns
+from . utils import BatchTransform, batch_transform
 
 __all__ = [
     'MovingAverage',