Added two C++ tutorials.
Alphabetized C++ Section.
Merge pull request #937 from Yohanna/C++-Tutorial

Added two C++ tutorials.
Sorting Flex section & minimal markdown fix
Remove a non-free book
Remove dead link
[en] Sorting Force section
adding language LUA
fix md books Lua
Merge pull request #938 from viniciusmo/master

Adding Lua pt_BR
[en] Sorting Forth section
Add Think OS book (greenteapress)
Merge pull request #939 from JIghtuse/master

Add Think OS book (greenteapress)
add book "Programming in Martin-Löf's Type Theory" by Bengt Nordström
Merge pull request #940 from AndriyLin/master

add book "Programming in Martin-Löf's Type Theory" by Bengt Nordström
Added OpenStack Operations Guide
Merge pull request #941 from marios-zindilis/master

Added OpenStack Operations Guide
[en] Sorting iOS section
Add 沉浸式学 Git http://igit.linuxtoy.org/index.html
Merge pull request #942 from viztor/patch-1

Add 沉浸式学 Git http://igit.linuxtoy.org/index.html