Fix typo and add a MIT license

100 Numpy exercises.ipynb

@@ -95,10 +95,14 @@
    ]
   },
   {
-   "cell_type": "markdown",
-   "metadata": {},
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
    "source": [
-    "$ `python -c \"import numpy; numpy.info(numpy.add)\"`"
+    "%run `python -c \"import numpy; numpy.info(numpy.add)\"`"
    ]
   },
   {
@@ -1247,7 +1251,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### 60. How to tell if a given 2D array has null columns? (★★☆)"
+    "#### 60. How to tell if a given 2D array has null columns? (★★☆)"
    ]
   },
   {

100 Numpy exercises.md

@@ -593,7 +593,7 @@ print(Z)
 print(Z[Z[:,1].argsort()])
 ```
 
-### 60. How to tell if a given 2D array has null columns? (★★☆)
+#### 60. How to tell if a given 2D array has null columns? (★★☆)
 
 
 ```python

README.md

@@ -12,3 +12,5 @@ those who teach.
 → [Read them on GitHub](100 Numpy exercises.md)  
 
 
+This work is licensed under a MIT license.
+