Enable clippy on CI

Add a clippy configuration file configuring the MSRV. Add a github
actions job to run clippy on CI.

Author: tcharding

.github/workflows/rust.yml

@@ -88,3 +88,19 @@ jobs:
           override: true
       - name: Create Doc
         run: cargo doc
+
+  Clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - run: rustup component add clippy
+      - uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+          args: --all-targets -- -D warnings

clippy.toml

@@ -0,0 +1 @@
+msrv = "1.41.1"