Update free-programming-books.md

Fixed typo.
markdown formatting to make url parsing easier

BAD : (http://www.jsoftware.com/books/pdf/calculus.pdf)(PDF)
GOOD: (http://www.jsoftware.com/books/pdf/calculus.pdf) (PDF)

BAD : ([PDF](http://www.kamishima.net/archive/mlmpyja.pdf), [EPUB](http://www.kamishima.net/archive/mlmpyja.epub))- 神嶌敏弘
GOOD: [PDF](http://www.kamishima.net/archive/mlmpyja.pdf), [EPUB](http://www.kamishima.net/archive/mlmpyja.epub) - 神嶌敏弘

BAD : (http://introcs.cs.princeton.edu/java/home/)- Robert
GOOD: (http://introcs.cs.princeton.edu/java/home/) - Robert
good/bad examples of adding book entries
Merge pull request #764 from borgified/url_fixes_easier_parsing

markdown formatting to make url parsing easier
Merge pull request #765 from borgified/update_contributing_format

good/bad examples of adding book entries
[en] Adding Perl Book (and removing Perl 6 duplicated)
Merge pull request #767 from esparta/master

[en] Adding Perl Book (and removing Perl 6 duplicated)
Sort scheme
Sort html/css
Sort iOS
Merge pull request #789 from Mouseion/patch-sort

Fix sorting
Update free-programming-books.md
[es] Adding .NET book
Merge branch 'master' of github.com:vhf/free-programming-books
Merge pull request #790 from wzhishen/master

added tutorial entries for Prolog
Merge pull request #791 from esparta/master

[es] New .NET book
[es] New Scala section with 2 book
Merge pull request #792 from esparta/master

[es] New Scala section with 2 book
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Merge pull request #793 from msdundar/patch-1

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