Fix CI by fixing version + add toolchain file (#52)

* Fix CI by fixing version + add toolchain file

* readme comment

* Tweak README message

* typo

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Co-authored-by: tyshkor <tyshko1@gmail.com>
Co-authored-by: Pratyush Mishra <pratyushmishra@berkeley.edu>

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: 1.67.0
           override: true
 
       # Install for Anvil
@@ -48,7 +48,7 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: 1.67.0
           override: true
           components: rustfmt, clippy
       - name: cargo fmt