Bump minimum Elixir version to 1.11

This is required now since the `property_table` dependency requires
Elixir 1.11 or later. Plus, it's time.

.circleci/config.yml

@@ -21,7 +21,7 @@ install_system_deps: &install_system_deps
 jobs:
   build_elixir_1_13_otp_24:
     docker:
-      - image: hexpm/elixir:1.13.2-erlang-24.2.1-alpine-3.15.0
+      - image: hexpm/elixir:1.13.4-erlang-24.3.3-alpine-3.15.3
     <<: *defaults
     steps:
       - checkout
@@ -66,34 +66,10 @@ jobs:
       - run: mix deps.get
       - run: mix test --exclude requires_ipv6
 
-  build_elixir_1_10_otp_23:
-    docker:
-      - image: hexpm/elixir:1.10.4-erlang-23.3.4-alpine-3.13.3
-    <<: *defaults
-    steps:
-      - checkout
-      - <<: *install_hex_rebar
-      - <<: *install_system_deps
-      - run: mix deps.get
-      - run: mix test --exclude requires_ipv6
-
-  build_elixir_1_9_otp_22:
-    docker:
-      - image: hexpm/elixir:1.9.4-erlang-22.3.4.18-alpine-3.13.3
-    <<: *defaults
-    steps:
-      - checkout
-      - <<: *install_hex_rebar
-      - <<: *install_system_deps
-      - run: mix deps.get
-      - run: mix test --exclude requires_ipv6
-
 workflows:
   version: 2
   build_test:
     jobs:
       - build_elixir_1_13_otp_24
       - build_elixir_1_12_otp_24
-      - build_elixir_1_11_otp_23
-      - build_elixir_1_10_otp_23
-      - build_elixir_1_9_otp_22
+      - build_elixir_1_11_otp_23

mix.exs

@@ -8,7 +8,7 @@ defmodule VintageNet.MixProject do
     [
       app: :vintage_net,
       version: @version,
-      elixir: "~> 1.9",
+      elixir: "~> 1.11",
       elixirc_paths: elixirc_paths(Mix.env()),
       test_coverage: [tool: ExCoveralls],
       start_permanent: Mix.env() == :prod,