Fix CI build

This bumps the MSRV to v1.42.0

Author: brendanzab

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: ["1.40.0", "stable", "beta", "nightly"]
+        rust: ["1.42.0", "stable", "beta", "nightly"]
     name: Check (${{ matrix.rust }})
     steps:
       - uses: actions/checkout@v2
@@ -35,7 +35,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: ["1.40.0", "stable", "beta", "nightly"]
+        rust: ["1.42.0", "stable", "beta", "nightly"]
     name: Test Suite (${{ matrix.rust }})
     steps:
       - uses: actions/checkout@v2
@@ -54,7 +54,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: ["1.40.0", "stable", "beta", "nightly"]
+        rust: ["1.42.0", "stable", "beta", "nightly"]
     name: Rustfmt (${{ matrix.rust }})
     steps:
       - uses: actions/checkout@v2
@@ -75,7 +75,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: ["1.40.0", "stable", "beta", "nightly"]
+        rust: ["1.42.0", "stable", "beta", "nightly"]
     name: Clippy (${{ matrix.rust }})
     steps:
       - uses: actions/checkout@v2