Migrate to Circleci (DataDog#109)

Migrate to Circleci and delete travis config

Author: gh123man

.circleci/config.yml

@@ -0,0 +1,46 @@
+version: 2 # use CircleCI 2.0
+
+x-dockerbuild-7: &dockerbuild-7
+  steps:
+    - checkout
+    - run: sudo docker-php-ext-install sockets
+    - run: find . -name '*.php' -exec php -l {} 1>/dev/null \; 2>/tmp/lint.err ; test ! -s /tmp/lint.err
+    - run: composer install --prefer-dist
+    - run: phpdbg -qrr  vendor/bin/phpunit --coverage-text
+    - run: composer lint
+
+x-dockerbuild-5: &dockerbuild-5
+  steps:
+    - checkout
+    - run: sudo docker-php-ext-install sockets
+    - run: find . -name '*.php' -exec php -l {} 1>/dev/null \; 2>/tmp/lint.err ; test ! -s /tmp/lint.err
+    - run: composer install --prefer-dist
+    - run: vendor/bin/phpunit --coverage-text
+    - run: composer lint
+
+jobs:
+  test-7.2:
+    <<: *dockerbuild-7
+    docker:
+      - image: circleci/php:7.2-node-browsers
+  test-7.1:
+    <<: *dockerbuild-7
+    docker:
+      - image: circleci/php:7.1-node-browsers
+  test-7.0:
+    <<: *dockerbuild-7
+    docker:
+      - image: circleci/php:7.0-node-browsers
+  test-5.6:
+    <<: *dockerbuild-5
+    docker:
+      - image: circleci/php:5.6-node-browsers
+
+workflows:
+  version: 2
+  check_compile:
+    jobs:
+      - test-7.2
+      - test-7.1
+      - test-7.0
+      - test-5.6