readme: move usage examples to tests

README contains an example like already exist in a example_test.go, so
example in a README was removed and example in tests has been updated:

- single example splitted to multiple examples for Connection methods
- added new examples for Ping(), Insert(), Delete(), Replace(),
  Update(), Call17(), Eval() and Connect()

Part of #123

Author: ligurio

README.md

@@ -177,117 +177,6 @@ will also be happy to provide advice or receive feedback.
 
 ## Usage
 
-```go
-package main
-
-import (
-	"github.com/tarantool/go-tarantool"
-	"log"
-	"time"
-)
-
-func main() {
-	spaceNo := uint32(512)
-	indexNo := uint32(0)
-
-	server := "127.0.0.1:3013"
-	opts := tarantool.Opts{
-		Timeout:       500 * time.Millisecond,
-		Reconnect:     1 * time.Second,
-		MaxReconnects: 3,
-		User:          "test",
-		Pass:          "test",
-	}
-	client, err := tarantool.Connect(server, opts)
-	if err != nil {
-		log.Fatalf("Failed to connect: %s", err.Error())
-	}
-
-	resp, err := client.Ping()
-	log.Println(resp.Code)
-	log.Println(resp.Data)
-	log.Println(err)
-
-	// insert new tuple { 10, 1 }
-	resp, err = client.Insert(spaceNo, []interface{}{uint(10), 1})
-    // or
-	resp, err = client.Insert("test", []interface{}{uint(10), 1})
-	log.Println("Insert")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// delete tuple with primary key { 10 }
-	resp, err = client.Delete(spaceNo, indexNo, []interface{}{uint(10)})
-    // or
-	resp, err = client.Delete("test", "primary", []interface{}{uint(10)})
-	log.Println("Delete")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// replace tuple with { 13, 1 }
-	resp, err = client.Replace(spaceNo, []interface{}{uint(13), 1})
-    // or
-	resp, err = client.Replace("test", []interface{}{uint(13), 1})
-	log.Println("Replace")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// update tuple with primary key { 13 }, incrementing second field by 3
-	resp, err = client.Update(spaceNo, indexNo, []interface{}{uint(13)}, []interface{}{[]interface{}{"+", 1, 3}})
-    // or
-	resp, err = client.Update("test", "primary", []interface{}{uint(13)}, []interface{}{[]interface{}{"+", 1, 3}})
-	log.Println("Update")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// insert tuple {15, 1} or increment second field by 1
-	resp, err = client.Upsert(spaceNo, []interface{}{uint(15), 1}, []interface{}{[]interface{}{"+", 1, 1}})
-    // or
-	resp, err = client.Upsert("test", []interface{}{uint(15), 1}, []interface{}{[]interface{}{"+", 1, 1}})
-	log.Println("Upsert")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// select just one tuple with primay key { 15 }
-	resp, err = client.Select(spaceNo, indexNo, 0, 1, tarantool.IterEq, []interface{}{uint(15)})
-    // or
-	resp, err = client.Select("test", "primary", 0, 1, tarantool.IterEq, []interface{}{uint(15)})
-	log.Println("Select")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// select tuples by condition ( primay key > 15 ) with offset 7 limit 5
-	// BTREE index supposed
-	resp, err = client.Select(spaceNo, indexNo, 7, 5, tarantool.IterGt, []interface{}{uint(15)})
-    // or
-	resp, err = client.Select("test", "primary", 7, 5, tarantool.IterGt, []interface{}{uint(15)})
-	log.Println("Select")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// call function 'func_name' with arguments
-	resp, err = client.Call("func_name", []interface{}{1, 2, 3})
-	log.Println("Call")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-
-	// run raw lua code
-	resp, err = client.Eval("return 1 + 2", []interface{}{})
-	log.Println("Eval")
-	log.Println("Error", err)
-	log.Println("Code", resp.Code)
-	log.Println("Data", resp.Data)
-}
-```
-
 To enable support of UUID in msgpack with [google/uuid](https://github.com/google/uuid),
 import tarantool/uuid submodule.
 ```go