Add. writer.async.lane
This writer create single linda for module and use them to communicate with all lindas
Implement async servers(Lane/ZMQ/UDP)
Each async writer can use existed async server or create new one.
```lua
require "log.writer.async.server.lane".run("inproc://main.logger",
  "return require 'log.writer.file.by_day'.new('./logs', 'events1.log', 6000)"
)

require "log.writer.async.server.lane".run("inproc://main.logger",
  "return require 'log.writer.file.by_day'.new('./logs', 'events2.log', 6000)"
)

local LOG = require"log".new(
  require "log.writer.async.lane".new("inproc://main.logger")
)
```
Merge branch 'master' into lane
Add compat module for zmq and lzmq.
Fix. bind/connect to multiply endpoint when use zmq module.
```lua
require "log.writer.net.zmq".new{"tcp://host1:123","tcp://host2:123"}
```
Clearer code.
Fix. logger.dump method
Update doc.
Update rockspec file for scm.