Update futures-preview requirement

Updates the requirements on [futures-preview](https://github.com/rust-lang-nursery/futures-rs) to permit the latest version.
- [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@0.3.0-alpha.18...0.3.0-alpha.19)

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

Cargo.toml

@@ -44,7 +44,7 @@ amadeus-parquet = { version = "=0.1.2", path = "amadeus-parquet", optional = tru
 amadeus-postgres = { version = "=0.1.2", path = "amadeus-postgres", optional = true }
 amadeus-serde = { version = "=0.1.2", path = "amadeus-serde", optional = true }
 constellation-rs = { version = "0.1", default-features = false, optional = true }
-futures-preview = "=0.3.0-alpha.18"
+futures-preview = "=0.3.0-alpha.19"
 serde = { version = "1.0", features = ["derive"] }
 serde_closure = "0.1"
 serde_traitobject = "0.1.6"

amadeus-aws/Cargo.toml

@@ -23,7 +23,7 @@ amadeus-core = { version = "=0.1.2", path = "../amadeus-core" }
 chrono = "0.4"
 flate2 = "1.0"
 futures-01 = { package = "futures", version = "0.1" }
-futures-preview = { version = "=0.3.0-alpha.18", features = ["compat"] }
+futures-preview = { version = "=0.3.0-alpha.19", features = ["compat"] }
 http = "0.1"
 once_cell = "1.0"
 rusoto_core = "0.40"

amadeus-core/Cargo.toml

@@ -20,7 +20,7 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 either = { version = "1.5", features = ["serde"] }
-futures-preview = "=0.3.0-alpha.18"
+futures-preview = "=0.3.0-alpha.19"
 owned_chars = "0.3"
 rand = "0.7"
 replace_with = "0.1"