Merge pull request #1414 from SuperStas/http2_explained_ru

Added HTTP2 Explained book (Ru)

free-programming-books-ru.md

@@ -47,6 +47,7 @@
 
 
 #### Networking
+* [Разъяснение HTTP2](https://github.com/vlet/http2-explained/blob/master/http2.ru.pdf?raw=true) (PDF) - Даниэль Штенберг
 * [TCP/IP Крупным планом](http://www.soslan.ru/tcp/)