fix ponctuation

docs/examples/notebooks/00_notebook_tour.ipynb

@@ -490,9 +490,9 b''
     {
      "cell_type": "markdown",
      "source": [
-      "Since IPython 0.13 image data Are by default embedded into the Image Object for compatibility with QtConsole and the ability to still be displayed offline.",
+      "Since IPython 0.13, image are embedded by default, for compatibility with QtConsole and the ability to still be displayed offline.",
       "",
-      "let's look at the differences:"
+      "Let's look at the differences:"
      ]
     },
     {