Removed "Artificial Intelligence A Modern Approach"

Definitely not free
Merge pull request #1235 from robschia/patch-1

Removed "Artificial Intelligence A Modern Approach"
added some books about Linux/C/PHP/Rails
Merge pull request #1236 from ruchee/master

added some books about Linux/C/PHP/Rails
Removed "How to Design Faceted Search"

Link to a "buy now" page with no signs of free stuff
New version of "A Course in Machine Learning"

Updated url
Merge pull request #1237 from robschia/patch-1

Removed "How to Design Faceted Search"
Merge pull request #1238 from robschia/patch-2

New version of "A Course in Machine Learning"