Update to rust 1.56.0 and 2021 edition (#637)

Cargo.toml

@@ -2,7 +2,7 @@
 name = "navi"
 version = "2.18.0"
 authors = ["Denis Isidoro <denis_isidoro@live.com>"]
-edition = "2018"
+edition = "2021"
 description = "An interactive cheatsheet tool for the command-line"
 homepage = "https://github.com/denisidoro/navi"
 documentation = "https://github.com/denisidoro/navi"

rust-toolchain.toml

@@ -0,0 +1,3 @@
+[toolchain]
+channel = "1.56.0"
+components = [ "rustfmt", "clippy" ]

src/config/cli.rs

@@ -217,28 +217,28 @@ mod tests {
     #[test]
     fn test_widget_possible_values() {
         for v in WIDGET_POSSIBLE_VALUES {
-            assert_eq!(true, Shell::from_str(v).is_ok())
+            assert!(Shell::from_str(v).is_ok())
         }
     }
 
     #[test]
     fn test_info_possible_values() {
         for v in INFO_POSSIBLE_VALUES {
-            assert_eq!(true, Info::from_str(v).is_ok())
+            assert!(Info::from_str(v).is_ok())
         }
     }
 
     #[test]
     fn test_func_possible_values() {
         for v in FUNC_POSSIBLE_VALUES {
-            assert_eq!(true, Func::from_str(v).is_ok())
+            assert!(Func::from_str(v).is_ok())
         }
     }
 
     #[test]
     fn test_finder_possible_values() {
         for v in FINDER_POSSIBLE_VALUES {
-            assert_eq!(true, FinderChoice::from_str(v).is_ok())
+            assert!(FinderChoice::from_str(v).is_ok())
         }
     }
 }