stable branch 1.2.x

[Maxim Dounin]

Hello!

First version of the 1.2.x stable branch has been released. 
The 1.2.0 version incorporates many new features developed in 
the 1.1.x branch, including the following:

- support for keepalive connections to upstream servers,
- consolidation of multiple simultaneous requests to upstream 
  servers if caching is used,
- support for multiple request and connection limits used 
  simultaneously,
- reduced memory consumption in various edge cases like 
  handling of long-lived requests.

Maxim Dounin