Update edition to 2021 (#286)

We don't use any feature but it feels right to be on it.

cli/Cargo.toml

@@ -10,7 +10,7 @@ homepage = "https://github.com/rust-ethereum/ethabi"
 keywords = ["ethereum", "eth", "abi", "solidity", "cli"]
 description = "Easy to use cli for conversion of ethereum contract calls to bytecode."
 license = "Apache-2.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 anyhow = "1"

contract/Cargo.toml

@@ -10,4 +10,4 @@ homepage = "https://github.com/rust-ethereum/ethabi"
 license = "MIT/Apache-2.0"
 keywords = ["ethereum", "eth", "abi", "solidity", "derive"]
 description = "Easy to use conversion of ethereum contract calls to bytecode."
-edition = "2018"
+edition = "2021"

derive/Cargo.toml

@@ -6,7 +6,7 @@ homepage = "https://github.com/paritytech/ethabi"
 license = "Apache-2.0"
 keywords = ["ethereum", "eth", "abi", "solidity", "derive"]
 description = "Easy to use conversion of ethereum contract calls to bytecode."
-edition = "2018"
+edition = "2021"
 
 [lib]
 proc-macro = true

ethabi/Cargo.toml

@@ -10,7 +10,7 @@ homepage = "https://github.com/rust-ethereum/ethabi"
 license = "Apache-2.0"
 keywords = ["ethereum", "eth", "abi", "solidity"]
 description = "Easy to use conversion of ethereum contract calls to bytecode."
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 hex = { version = "0.4", default-features = false, features = ["alloc"] }

rustfmt.toml

@@ -1,4 +1,4 @@
 hard_tabs = true
 max_width = 120
 use_small_heuristics = "Max"
-edition = "2018"
+edition = "2021"

tests/Cargo.toml

@@ -2,7 +2,7 @@
 name = "ethabi-tests"
 version = "0.1.1"
 authors = ["debris <marek.kotewicz@gmail.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 ethabi = { path = "../ethabi" }