Move to CircleCI from Travis-CI

CircleCI works even better as far as integrating into the repo, and on
the plus side provides direct Docker image support so we can utilize an
image that has clang v4.0 pre-installed on it where it turned out to be
near impossible to get a working release build on the ancient images
used in Travis-CI.

Author: Arcanemagus

.circleci/config.yml

@@ -0,0 +1,19 @@
+version: 2
+jobs:
+  build:
+    working_directory: ~/linter-clang
+    docker:
+      - image: walberla/buildenv-ubuntu-clang:4.0
+        environment:
+          DISPLAY: ":99"
+    steps:
+      - run: apt-get update
+      # Install some pre-requisite packages and missing dependencies from the atom package
+      - run: apt-get --assume-yes --quiet --no-install-suggests --no-install-recommends install sudo xvfb libxss1 libasound2
+      # Fire up a VFB to run Atom in
+      - run: /sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x16
+      - checkout
+      # Download and run the (modified) Atom CI script
+      - run: curl -s -O https://raw.githubusercontent.com/Arcanemagus/ci/atomlinter/build-package.sh
+      - run: chmod u+x build-package.sh
+      - run: ./build-package.sh