Support Rails 6 (#595)

.travis.yml

@@ -4,6 +4,7 @@ rvm:
 - 2.2.7
 - 2.3.4
 - 2.4.1
+- 2.6.0
 - ruby-head
 matrix:
   allow_failures:

annotate.gemspec

@@ -44,5 +44,5 @@ Gem::Specification.new do |s|
 
   s.specification_version = 4 if s.respond_to? :specification_version
   s.add_runtime_dependency(%q<rake>, ['>= 10.4', '< 13.0'])
-  s.add_runtime_dependency(%q<activerecord>, ['>= 3.2', '< 6.0'])
+  s.add_runtime_dependency(%q<activerecord>, ['>= 3.2', '< 7.0'])
 end