Use crates.io version of futures-preview and patch it

This allows us to publish our library on crates.io, which wouldn't be possible with a git dependency. The library also compiles with the unpatched version since only the async-await binary use futures.

Author: phil-opp

Cargo.toml

@@ -43,12 +43,15 @@ default-features = false
 features = ["unicode"]
 
 [dependencies.futures-preview]
-git = "https://github.com/phil-opp/futures-rs.git"
-branch = "alloc"
+version = "0.3.0-alpha"
 default-features = false
 features = ["alloc"]
 
 [profile.release]
 codegen-units = 1 # better optimizations
 debug = true
 lto = true # better optimizations
+
+[patch.crates-io.futures-preview]
+git = "https://github.com/phil-opp/futures-rs.git"
+branch = "alloc"