Initial removal of english books from chinese(zh) books list.
Removal decisions were made comparing it with the english(en) books list; itens with the exact same link were removed.
Further removal may need a more careful consideration, since for some reason these book's titles were translated to chinese in the *zh* list.
Added 3 chinese(zh) books.
Add Explore Flask book (crowdfunded)
Merge pull request #451 from JIghtuse/master

Add Explore Flask book (crowdfunded)
Add a ruby on rails metaprogramming book

Added "Kestrels, Quirky Birds, and Hopeless Egocentricity" under the Ruby on Rails.
Merge pull request #452 from sbagdat/patch-1

Add a ruby on rails metaprogramming book
Added two Tcl books
Merge pull request #453 from tpoindex/patch-1

Added two Tcl books
Added "A Course in Machine Learning"
Merge pull request #454 from bbuyukguzel/master

Added "A Course in Machine Learning"
Add Arduino
Merge pull request #455 from hiseba/patch-1

Adding Arduino
Add a coffeescript book
Merge pull request #456 from sbagdat/patch-1

Add a coffeescript book
Some changes

- Removed "A Course in Machine Learning". There were 2 same links in the
list. One of them kept which is originally belong the author
- Added 1 Android and 2 Powershell books
Merge pull request #457 from bbuyukguzel/master

Some changes
Merge pull request #447 from jgpacker/master

Initial removal of english books from chinese(zh) books list.
Update free-programming-books.md
added Twitter share button

I couldn't add a Facebook share button because I don't have an account but here is the link if someone else wants to add it:

https://developers.facebook.com/docs/plugins/like-button/
Merge pull request #459 from breakingcrypto/patch-1

added Twitter share button
Merge pull request #458 from murphyrandle/master

Update free-programming-books.md