Update TravisCI config to inclue Ruby 2.7

HarlemSquirrel · HarlemSquirrel · commit bef425743abb · 2020-02-01T15:02:20.000-05:00
diff --git a/.travis.yml b/.travis.yml
@@ -7,6 +7,7 @@ rvm:
   - 2.4
   - 2.5
   - 2.6
+  - 2.7
   # optional
   - ruby-head
   - jruby-19mode
