Upgrade TLS in documentation and examples (#433)

Author: Anaethelion

README.md

@@ -159,7 +159,7 @@ cfg := elasticsearch.Config{
     MaxIdleConnsPerHost:   10,
     ResponseHeaderTimeout: time.Second,
     TLSClientConfig: &tls.Config{
-      MinVersion: tls.VersionTLS11,
+      MinVersion: tls.VersionTLS12,
       // ...
     },
     // ...

_examples/configuration.go

@@ -45,7 +45,7 @@ func main() {
 			ResponseHeaderTimeout: time.Millisecond,
 			DialContext:           (&net.Dialer{Timeout: time.Nanosecond}).DialContext,
 			TLSClientConfig: &tls.Config{
-				MinVersion: tls.VersionTLS11,
+				MinVersion: tls.VersionTLS12,
 				// ...
 			},
 		},

doc.go

@@ -39,7 +39,7 @@ To configure the client, pass a Config object to the NewClient function:
 		    ResponseHeaderTimeout: time.Second,
 		    DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
 		    TLSClientConfig: &tls.Config{
-		      MinVersion:         tls.VersionTLS11,
+		      MinVersion:         tls.VersionTLS12,
 		    },
 		  },
 		}

elasticsearch_example_test.go

@@ -63,7 +63,7 @@ func ExampleNewClient() {
 			ResponseHeaderTimeout: time.Second,
 			DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
 			TLSClientConfig: &tls.Config{
-				MinVersion: tls.VersionTLS11,
+				MinVersion: tls.VersionTLS12,
 			},
 		},
 	}

elasticsearch_integration_test.go

@@ -140,7 +140,7 @@ func TestClientTransport(t *testing.T) {
 				ResponseHeaderTimeout: time.Second,
 				DialContext:           (&net.Dialer{Timeout: time.Nanosecond}).DialContext,
 				TLSClientConfig: &tls.Config{
-					MinVersion:         tls.VersionTLS11,
+					MinVersion:         tls.VersionTLS12,
 					InsecureSkipVerify: true,
 				},
 			},