Bump minimum supported Rust version to 1.20

Author: hcpl

README.md

@@ -5,7 +5,7 @@
 Syntax extensions to automatically derive `FromSql` and `ToSql` implementations for Postgres enum,
 domain, and composite types.
 
-The generated code requires rust-postgres 0.14 or 0.15 and Rust 1.15.0 or higher.
+The generated code requires rust-postgres 0.14 or 0.15 and Rust 1.20.0 or higher.
 
 # Usage
 

circle.yml

@@ -3,7 +3,7 @@ jobs:
   build:
     working_directory: ~/build
     docker:
-      - image: jimmycuadra/rust:1.19.0
+      - image: jimmycuadra/rust:1.20.0
       - image: postgres:9.6
         environment:
           POSTGRES_PASSWORD: password
@@ -17,10 +17,10 @@ jobs:
           paths:
             - ~/.cargo/registry/index
       - restore_cache:
-          key: dependencies-1.19-{{ checksum "Cargo.lock" }}
+          key: dependencies-1.20-{{ checksum "Cargo.lock" }}
       - run: cargo test
       - save_cache:
-          key: dependencies-1.19-{{ checksum "Cargo.lock" }}
+          key: dependencies-1.20-{{ checksum "Cargo.lock" }}
           paths:
             - target
             - ~/.cargo/registry/cache