Use emacs-travis.mk instead of deprecated evm

Also add emacs-26-pretest and emacs-snapshot to build matrix.

Author: juergenhoetzel

.travis.yml

@@ -1,20 +1,40 @@
-language: csharp
+language: emacs-lisp
+# Emacs fails to build in container-based builds on Travis
+# See https://github.com/travis-ci/travis-ci/issues/9061
+# and https://github.com/moby/moby/issues/22801
 sudo: required
-
-before_install:
-  - sudo apt-get install -y fsharp
-  - curl -fsSkL https://gist.github.com/rejeep/ebcd57c3af83b049833b/raw > x.sh && source ./x.sh
-  - evm install $EVM_EMACS --use --skip
-
-env:
-  - EVM_EMACS=emacs-25.1-travis
-  - EVM_EMACS=emacs-25.2-travis
-
+dist: trusty
+cache:
+  - directories:
+      # Cache stable Emacs binaries (saves 1min per job)
+      - "$HOME/emacs/"
+# Allow Emacs snapshot builds to fail and don’t wait for these as they can take
+# a looooong time
 matrix:
   fast_finish: true
   allow_failures:
-    env:
-      - EVM_EMACS=emacs-git-snapshot-travis
+    - env: EMACS_VERSION=snapshot
+env:
+  - EMACS_VERSION=25.1
+  - EMACS_VERSION=25.2
+  - EMACS_VERSION=25.3
+  - EMACS_VERSION=26.0.91 PRETEST=yes
+  - EMACS_VERSION=snapshot
+
+before_install:
+  # Add mono repo
+  - sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+  - echo "deb http://download.mono-project.com/repo/ubuntu stable-trusty main" | sudo tee /etc/apt/sources.list.d/mono-official-stable.list
+  - sudo apt-get -qq update
+  - sudo apt-get install -y mono-devel 
+  # Configure $PATH: Executables are installed to $HOME/bin
+  - export PATH="$HOME/bin:$PATH"
+  # Download the makefile to emacs-travis.mk
+  - wget 'https://raw.githubusercontent.com/flycheck/emacs-travis/master/emacs-travis.mk'
+  # Install Emacs (according to $EMACS_VERSION) and Cask
+  - make -f emacs-travis.mk install_emacs
+  - make -f emacs-travis.mk install_cask
+  - sudo apt-get install -y fsharp mono-xbuild
 
 script:
   - make test-all