Lock bundler to 1.17.3

deivid-rodriguez · deivid-rodriguez · commit b36567373ee5 · 2019-03-19T17:24:05.000+01:00
Since it's the last version supporting the full current CI matrix.
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,6 @@
 before_install:
   - gem update --system 2.7.9
-  - gem install bundler
+  - gem install bundler:1.17.3
   - rvm @global do gem uninstall did_you_mean
 bundler_args: --without development
 language: ruby
