readme: update section about installation

Go 1.3 mentioned in installation section was EOLed many years ago. No
sense to describe it's installation. Go 1.3 replaced with Go 1.13. Go
1.13 is outdated too and unsupported, but we run tests with it in Github
Actions so it is a guarantee that everything will works with it.

Part of #123

Author: ligurio

README.md

@@ -31,33 +31,26 @@ faster than other packages according to public benchmarks.
 
 ## Installation
 
-We assume that you have Tarantool version 1.6 and a modern Linux or BSD
+We assume that you have Tarantool version 1.6+ and a modern Linux or BSD
 operating system.
 
-You will need a current version of `go`, version 1.3 or later (use
-`go version` to check the version number). Do not use `gccgo-go`.
+You need a current version of `go`, version 1.13 or later (use `go version` to
+check the version number). Do not use `gccgo-go`.
 
-**Note:** If your `go` version is younger than 1.3, or if `go` is not installed,
-download the latest tarball from [golang.org](https://golang.org/dl/) and say:
+**Note:** If your `go` version is older than 1.3 or if `go` is not installed,
+download and run the latest tarball from [golang.org][golang-dl].
 
-```bash
-$ sudo tar -C /usr/local -xzf go1.7.5.linux-amd64.tar.gz
-$ export PATH=$PATH:/usr/local/go/bin
-$ export GOPATH="/usr/local/go/go-tarantool"
-$ sudo chmod -R a+rwx /usr/local/go </pre>
-```
-
-The `go-tarantool` package is in
-[tarantool/go-tarantool](github.com/tarantool/go-tarantool) repository.
-To download and install, say:
+The package `go-tarantool` is located in [tarantool/go-tarantool][go-tarantool]
+repository. To download and install, say:
 
 ```
 $ go get github.com/tarantool/go-tarantool
 ```
 
-This should bring source and binary files into subdirectories of `/usr/local/go`,
-making it possible to access by adding `github.com/tarantool/go-tarantool` in
-the `import {...}` section at the start of any Go program.
+This should put the source and binary files in subdirectories of
+`/usr/local/go`, so that you can access them by adding
+`github.com/tarantool/go-tarantool` to the `import {...}` section at the start
+of any Go program.
 
 <h2>Hello World</h2>
 
@@ -217,3 +210,5 @@ See feature comparison in [documentation](https://www.tarantool.io/en/doc/latest
 [discussions-url]: https://github.com/tarantool/tarantool/discussions
 [stackoverflow-badge]: https://img.shields.io/badge/stackoverflow-tarantool-orange.svg
 [stackoverflow-url]: https://stackoverflow.com/questions/tagged/tarantool
+[golang-dl]: https://go.dev/dl/
+[go-tarantool]: https://github.com/tarantool/go-tarantool