Add .travis.yml file

.travis.yml

@@ -0,0 +1,13 @@
+language: nix
+
+install:
+  - bash <(curl https://raw.githubusercontent.com/purcell/nix-emacs-ci/master/travis-install)
+
+env:
+  - EMACS_CI=emacs-25-3
+  - EMACS_CI=emacs-26-3
+
+script:
+  - emacs --version
+  - make ci-dependencies
+  - make check