Use stable PyO3

.github/workflows/python.yml

@@ -48,7 +48,7 @@ jobs:
       - name: Set up Rust
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly-2019-07-19
+          toolchain: stable
           profile: minimal
           default: true
       - name: Build native module

python/Cargo.toml

@@ -12,5 +12,5 @@ crate-type = ["cdylib"]
 [dependencies]
 hyperbuild = "0.1.4"
 [dependencies.pyo3]
-version = "=0.9.0-alpha.1"
+version = "0.11.1"
 features = ["extension-module"]