Update free-courses-en.md

Added Python course by MIT

free-courses-en.md

@@ -68,7 +68,7 @@
 ###Python
 * [Berkeley's Structure and Interpretation of Computer Programs](http://www-inst.eecs.berkeley.edu/~cs61a/)
 * [Google's Python Course](https://developers.google.com/edu/python/)
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+* [Introduction to Computer Science and Programming](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-00sc-introduction-to-computer-science-and-programming-spring-2011/) (MIT's opencourseware)
 
 ###Ruby
 * [RubyMonk - Interactive Ruby tutorials](http://rubymonk.com)