Bump MSRV up to 1.55.0

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ on:
 name: CI
 
 env:
-  rust: 1.50.0
+  rust: 1.55.0
 
 jobs:
   partial_unit_tests:

.github/workflows/integration.yml

@@ -8,7 +8,7 @@ on:
 name: Integration Tests
 
 env:
-  rust: 1.50.0
+  rust: 1.55.0
 
 jobs:
   shell_tests:

.travis.yml

@@ -41,7 +41,7 @@ addons:
     - zlib1g-dev
 
 rust:
-  - 1.50.0
+  - 1.55.0
 
 cache:
   npm: true

README.md

@@ -9,7 +9,7 @@
 [![Docs.rs](https://docs.rs/exonum/badge.svg)](https://docs.rs/exonum)
 [![License: Apache-2.0](https://img.shields.io/github/license/exonum/exonum.svg)](LICENSE.md)
 [![LoC](https://tokei.rs/b1/github/exonum/exonum)](https://github.com/exonum/exonum)
-![rust 1.50.0+ required](https://img.shields.io/badge/rust-1.50.0+-blue.svg?label=Required%20Rust)
+![rust 1.55.0+ required](https://img.shields.io/badge/rust-1.55.0+-blue.svg?label=Required%20Rust)
 
 **Community:**
 [![Join the chat at https://gitter.im/exonum/exonum](https://img.shields.io/gitter/room/exonum/exonum.svg?label=Chat)](https://gitter.im/exonum/exonum)

test-suite/testkit/README.md

@@ -3,7 +3,7 @@
 [![Travis Build Status](https://img.shields.io/travis/exonum/exonum/master.svg?label=Linux%20Build)](https://travis-ci.com/exonum/exonum)
 [![Docs.rs](https://docs.rs/exonum-testkit/badge.svg)](https://docs.rs/exonum-testkit)
 [![License: Apache-2.0](https://img.shields.io/github/license/exonum/exonum.svg)](https://github.com/exonum/exonum/blob/master/LICENSE)
-![rust 1.50.0+ required](https://img.shields.io/badge/rust-1.50.0+-blue.svg?label=Required%20Rust)
+![rust 1.55.0+ required](https://img.shields.io/badge/rust-1.55.0+-blue.svg?label=Required%20Rust)
 
 Testkit for Exonum blockchain allows to test service operation.
 Specifically, it allows to test transaction execution