Expose some detail implement : sockets::sockaddr_cast.
And add 1 more interface :
  sockets::sockaddr_in_cast
Modify the constructor of Buffer to : explicit Buffer(size_t initialSize = kInitialSize)
Add a parameter to indicate the initial memory block size
Merge pull request #77 from weizili/patch-Buffer2

Modify the constructor of Buffer
Merge pull request #69 from weizili/patch-SocketsOps

Expose some detail implement : sockets::sockaddr_cast.
Add more interface for EventLoopThreadPool:
  EventLoop* getLoopForHash(size_t hashCode);
  bool started() const;

On some occasions, we need to process some tasks with the same type
always in the same working thread.
Add enable_testing() to CMakeLists.txt.
And add the following existing unit test to cmake test system:
  atomic_unittest
  date_unittest
  exception_test
  fileutil_test
  gzipfile_test
  logstream_test
  timestamp_unittest
  timezone_unittest
  buffer_unittest
  buffer_cpp11_unittest
  inetaddress_unittest
Merge pull request #78 from weizili/patch-EventLoopThreadPool2

Add getLoopForHash() in EventLoopThreadPool
Merge pull request #79 from weizili/patch-enable_testing2

Add enable_testing() to CMakeLists.txt.