Add travis integration

.travis.yml

@@ -0,0 +1,28 @@
+language: emacs-lisp
+sudo: false
+cache:
+  - directories:
+      - "$HOME/emacs/"
+matrix:
+  fast_finish: true
+  allow_failures:
+    - env: EMACS_VERSION=snapshot
+env:
+  - EMACS_VERSION=25.1
+  # 25.2 is identical to 25.3 except for a security bug
+  - EMACS_VERSION=25.3
+  - EMACS_VERSION=snapshot
+before_install:
+  - export PATH="$HOME/bin:$PATH"
+  - wget 'https://raw.githubusercontent.com/flycheck/emacs-travis/master/emacs-travis.mk'
+  - make -f emacs-travis.mk install_emacs
+  - make -f emacs-travis.mk install_cask
+install:
+  - cask install
+script:
+  - make compile
+  - make lint
+notifications:
+  email:
+    # Default is change, but that includes a new branch's 1st success.
+    on_success: never