Formatting fixes:

Added empty line before heading "Information Retrieval" to fix html output.
Untabified one line in Python section.

free-programming-books.md

@@ -283,6 +283,7 @@
 * [The Architecture of Open Source Applications: Vol. 1: Elegance, Evolution, and a Few Fearless Hacks; Vol. 2: Structure, Scale, and a Few More Feerless Hacks](http://www.aosabook.org/en/index.html)
 * [The Performance of Open Source Applications](http://aosabook.org/en/)
 * [The Future of Ideas](http://the-future-of-ideas.com/download/lessig_FOI.pdf)
+
 ####Information Retrieval
 * [Introduction to Information Retrieval](http://nlp.stanford.edu/IR-book/information-retrieval-book.html)
 * [Information Retrieval: A Survey](http://www.csee.umbc.edu/csee/research/cadip/readings/IR.report.120600.book.pdf) (PDF)