Support closing stream (#877)

* Support closing stream

In this version, we can close stream as following:

```ruby
client = Twitter::Streaming::Client.new do |config|
  # Set up configuration
end

t = Thread.new do
  client.filter(track: keyword) do |object|
    # process object
  end
end

Signal.trap(:TERM) do
  # terminate process silently
  client.close
  exit true
end
```

* Add Twitter::Streaming::Connection#stream spec

* Wait for connection

* Suppress rubocop warning

    lib/twitter/streaming/connection.rb:17:7: C: Method has too many lines. [13/10]
          def stream(request, response) ...
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* Use port number 8443 instead of 11443

Because rubocop reports following warnings:

    spec/twitter/streaming/connection_spec.rb:88:48: C: Use underscores(_) as decimal mark and separate every 3 digits with them.
        let(:client) {  TCPSocket.new('127.0.0.1', 11443) }
                                                   ^^^^^
    spec/twitter/streaming/connection_spec.rb:94:44: C: Use underscores(_) as decimal mark and separate every 3 digits with them.
          @server = TCPServer.new('127.0.0.1', 11443)
                                               ^^^^^

lib/twitter/streaming/client.rb

@@ -105,6 +105,10 @@ def before_request(&block)
         end
       end
 
+      def close
+        @connection.close
+      end
+
     private
 
       def request(method, uri, params)

lib/twitter/streaming/connection.rb

@@ -11,14 +11,23 @@ def initialize(options = {})
         @tcp_socket_class = options.fetch(:tcp_socket_class) { TCPSocket }
         @ssl_socket_class = options.fetch(:ssl_socket_class) { OpenSSL::SSL::SSLSocket }
         @using_ssl        = options.fetch(:using_ssl)        { false }
+        @write_pipe = nil
       end
 
-      def stream(request, response)
+      def stream(request, response) # rubocop:disable MethodLength
         client = connect(request)
         request.stream(client)
-        while body = client.readpartial(1024) # rubocop:disable AssignmentInCondition
-          response << body
+        read_pipe, @write_pipe = IO.pipe
+        loop do
+          read_ios, _write_ios, _exception_ios = IO.select([read_pipe, client])
+          case read_ios.first
+          when client
+            response << client.readpartial(1024)
+          when read_pipe
+            break
+          end
         end
+        client.close
       end
 
       def connect(request)
@@ -30,6 +39,10 @@ def connect(request)
         ssl_client.connect
       end
 
+      def close
+        @write_pipe.write('q') if @write_pipe
+      end
+
     private
 
       def new_tcp_socket(host, port)

spec/twitter/streaming/connection_spec.rb

@@ -77,4 +77,41 @@ def <<(data); end
       end
     end
   end
+
+  describe 'stream' do
+    subject(:connection) do
+      Twitter::Streaming::Connection.new(tcp_socket_class: DummyTCPSocket, ssl_socket_class: DummySSLSocket)
+    end
+
+    let(:method) { :get }
+    let(:uri)    { 'https://stream.twitter.com:443/1.1/statuses/sample.json' }
+    let(:client) {  TCPSocket.new('127.0.0.1', 8443) }
+
+    let(:request) { HTTP::Request.new(verb: method, uri: uri) }
+    let(:response) { DummyResponse.new {} }
+
+    before do
+      @server = TCPServer.new('127.0.0.1', 8443)
+    end
+
+    after do
+      @server.close
+    end
+
+    it 'close stream' do
+      expect(connection).to receive(:connect).with(request).and_return(client)
+      expect(request).to receive(:stream).with(client)
+
+      stream_closed = false
+      t = Thread.start do
+        connection.stream(request, response)
+        stream_closed = true
+      end
+      expect(stream_closed).to be false
+      sleep 1
+      connection.close
+      t.join
+      expect(stream_closed).to be true
+    end
+  end
 end