Rust1.46 and nightly ci (#246)

.github/workflows/ci.yml

@@ -14,8 +14,10 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        rust: [nightly, stable]
 
     runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ matrix.rust == 'nightly' }}
 
     steps:
     - uses: actions/checkout@v2
@@ -23,7 +25,8 @@ jobs:
     - name: Install Rust
       uses: actions-rs/toolchain@v1
       with:
-        toolchain: stable
+        toolchain: ${{ matrix.rust }}
+        default: true
         profile: minimal
         components: clippy