Bump futures from 0.1.29 to 0.3.1

Bumps [futures](https://github.com/rust-lang-nursery/futures-rs) from 0.1.29 to 0.3.1.
- [Release notes](https://github.com/rust-lang-nursery/futures-rs/releases)
- [Changelog](https://github.com/rust-lang-nursery/futures-rs/blob/master/CHANGELOG.md)
- [Commits](rust-lang/futures-rs@0.1.29...0.3.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

Cargo.lock

@@ -5,7 +5,7 @@ authors = ["debris <marek.kotewicz@gmail.com>", "snd <kruemaxi@gmail.com>"]
 
 [dependencies]
 bridge-contracts = { path = "../contracts" }
-futures = "0.1"
+futures = "0.3"
 serde = "1.0"
 serde_derive = "1.0"
 serde_json = "1.0"

bridge/Cargo.toml

@@ -15,5 +15,5 @@ tokio-core = "0.1.8"
 docopt = "1.0"
 log = "0.4"
 env_logger = "0.7"
-futures = "0.1.14"
+futures = "0.3.1"
 web3 = { git = "https://github.com/tomusdrw/rust-web3" }

cli/Cargo.toml

@@ -15,5 +15,5 @@ tokio-core = "0.1.8"
 docopt = "1.0"
 log = "0.4"
 env_logger = "0.7"
-futures = "0.1.14"
+futures = "0.3.1"
 web3 = { git = "https://github.com/tomusdrw/rust-web3" }

deploy/Cargo.toml

@@ -8,7 +8,7 @@ bridge = { path = "../bridge" }
 bridge-contracts = { path = "../contracts", features = ["integration-tests"] }
 ethabi = "9.0"
 ethereum-types = "0.8"
-futures = "0.1"
+futures = "0.3"
 jsonrpc-core = "14.0"
 pretty_assertions = "0.6.1"
 rustc-hex = "2.0"