Bump Rust edition

Drop support for Rust 1.43.0. This was required when the JSONPath
comparison project pinned Rust to that version, but now that project
uses the latest stable Rust.

Author: glyn

Diff for: .github/workflows/quickstart.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        toolchain: [ stable, "1.43.0" ]
+        toolchain: [ stable ]
     steps:
       - name: Checkout sources
         uses: actions/checkout@v2
@@ -38,7 +38,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        toolchain: [ stable, "1.43.0" ]
+        toolchain: [ stable ]
     steps:
       - name: Checkout sources
         uses: actions/checkout@v2

Diff for: Cargo.toml

@@ -2,7 +2,7 @@
 name = "jsonpath_reference_implementation"
 version = "0.0.1"
 authors = ["Glyn Normington <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 itertools = "0.9.0"