.travis.yml in hpsqrt-1.5.0 vs .travis.yml in hpsqrt-1.6.0

@@ -1,6 +1,7 @@
 ---
 language: ruby
 cache: bundler
 rvm:
-  - 2.7.0
-before_install: gem install bundler -v 2.1.0.pre.1
+  - 2.6.3
+before_install:
+  - gem install bundler -v '~> 2.0.1'