Fix race in destroying of service manager.

Service connection retrives shared_ptr to own service manager in destructor, that sometimes may lead to removing of service manager from its own thread. Now service connection uses service manager via reference.
WARNING: Now user must remove all connections before removing of corresponding service manager.
WARNING: This commit breaks binary compatibility.
Fix build on Mac.

 - dropped some unused variables.
 - workaround about libev++ conflicting with EV_ERROR variable declared in <event.h>
 - forgotten include.
Exterminating useless statement.
Merge pull request #9 from 3Hren/v0.11

Fix build on Mac.
Add new dependecies.

Now cocaine::asio uses Boost.Asio, which requires linking with Boost.System.
Fixed null pointer dereference.

Using of m_connection and moving it in the same statement is a bad idea.
Bump version - 0.11.1.0.