Update CI

Author: sebastianvarela

.travis.yml

@@ -1,5 +1,13 @@
 language: swift
-osx_image: xcode10.2
+osx_image: xcode11.6
+
+addons:
+  homebrew:
+    brewfile: true
+
+cache:
+  bundler: true
+
 script:
 - set -o pipefail
 - swift --version