Update free-programming-books.md

Added Parrot/Perl 6 > Perl 6 Programming @ Wikibooks.org
Adding tryF#
Merge pull request #674 from Andrea/patch-1

Adding tryF#
Merge pull request #673 from DavMorr/patch-1

Update free-programming-books.md
Merge pull request #672 from marios-zindilis/master

Added two books on PicoLisp