Fix ActiveRecord version check (#956)

* Fix ActiveRecord version check

* Update changelog for #956

* Simplify ActiveRecord version check

CHANGELOG.md

@@ -16,7 +16,8 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Fixed
 
-- None
+- [#956](https://github.com/airblade/paper_trail/pull/956) -
+  Fix ActiveRecord >= 5.1 version check 
 
 ## 7.0.1 (2017-04-10)
 

lib/paper_trail/record_trail.rb

@@ -1,7 +1,8 @@
 module PaperTrail
   # Represents the "paper trail" for a single record.
   class RecordTrail
-    RAILS_GTE_5_1 = ::ActiveRecord::VERSION::MAJOR >= 5 && ::ActiveRecord::VERSION::MINOR >= 1
+    RAILS_GTE_5_1 = ::ActiveRecord.respond_to?(:gem_version) &&
+      ::ActiveRecord.gem_version >= ::Gem::Version.new("5.1.0.beta1")
 
     def initialize(record)
       @record = record