add __init__ file for colors tests and editted __init__ in plotly.py/plotly dir

Author: Kully

plotly/__init__.py

@@ -29,5 +29,5 @@
 from __future__ import absolute_import
 
 from plotly import (plotly, graph_objs, grid_objs, tools, utils, session,
-                    offline)
+                    offline, colors)
 from plotly.version import __version__

plotly/tests/test_core/test_colors/__init__.py

@@ -4,7 +4,7 @@
 from nose.tools import raises
 import plotly.tools as tls
 from plotly.exceptions import PlotlyError
-from plotly import colors
+import plotly.colors as colors
 
 """
 class TestColors(TestCase):