Remove CircleCI (#915)

None of the platforms that use it are supported right now, so it seems
silly to fail builds for other platforms when these ones can't possibly
succeed.

This should be reverted in stages as the platforms regain support.

.circleci/config.yml

@@ -1,56 +0,0 @@
-version: 2
-
-jobs:
-
-  android-test:
-    working_directory: ~/winit
-    docker:
-      - image: tomaka/cargo-apk
-    steps:
-      - run: apt-get -qq update && apt-get install -y git
-      - checkout
-      - restore_cache:
-          key: android-test-cache-{{ checksum "Cargo.toml" }}
-      - run: cargo apk build --example window
-      - save_cache:
-          key: android-test-cache-{{ checksum "Cargo.toml" }}
-          paths:
-            - target
-
-  asmjs-test:
-    working_directory: ~/winit
-    docker:
-      - image: tomaka/rustc-emscripten
-    steps:
-      - run: apt-get -qq update && apt-get install -y git
-      - checkout
-      - restore_cache:
-          key: asmjs-test-cache-{{ checksum "Cargo.toml" }}
-      - run: cargo build --example window --target asmjs-unknown-emscripten
-      - save_cache:
-          key: asmjs-test-cache-{{ checksum "Cargo.toml" }}
-          paths:
-            - target
-
-  wasm-test:
-    working_directory: ~/winit
-    docker:
-      - image: tomaka/rustc-emscripten
-    steps:
-      - run: apt-get -qq update && apt-get install -y git
-      - checkout
-      - restore_cache:
-          key: wasm-test-cache-{{ checksum "Cargo.toml" }}
-      - run: cargo build --example window --target wasm32-unknown-emscripten
-      - save_cache:
-          key: wasm-test-cache-{{ checksum "Cargo.toml" }}
-          paths:
-            - target
-  
-workflows:
-  version: 2
-  build-test-and-deploy:
-    jobs:
-      - android-test
-      - asmjs-test
-      - wasm-test