Fixing necessary imports for 2d-denstiy string doc examples

Author: Kully

plotly/tools.py

@@ -1515,6 +1515,8 @@ def create_2D_density(x, y, colorscale='Earth', ncontours=20,
         import plotly.plotly as py
         from plotly.tools import FigureFactory as FF
 
+        import numpy as np
+
         # Make data points
         t = np.linspace(-1,1.2,2000)
         x = (t**3)+(0.3*np.random.randn(2000))
@@ -1532,6 +1534,8 @@ def create_2D_density(x, y, colorscale='Earth', ncontours=20,
         import plotly.plotly as py
         from plotly.tools import FigureFactory as FF
 
+        import numpy as np
+
         # Make data points
         t = np.linspace(-1,1.2,2000)
         x = (t**3)+(0.3*np.random.randn(2000))