Add custom comparison for Montrose::Recurrence

In the same vein as adding `Montrose::Schedule#==`

This allows `Montrose::Recurrence` objects to be compared by their
underlying hash options.

lib/montrose/recurrence.rb

@@ -407,6 +407,19 @@ def later?(timestamp)
       ends_at && timestamp > ends_at
     end
 
+    # Return true/false if hash configuration is equal to
+    # the other given recurrence's hash configuration
+    #
+    # @return [Boolean] whether or not the other's hash matches
+    #
+    def ==(other)
+      if other.is_a?(self.class) || other.is_a?(Hash)
+        to_hash == other.to_hash
+      else
+        super
+      end
+    end
+
     private
 
     def event_enum

spec/montrose/recurrence_spec.rb

@@ -100,6 +100,19 @@
     end
   end
 
+  describe "#==" do
+    it "compares the recurrence with another recurrence" do
+      options = {every: :day, total: 3, starts: now, interval: 1}
+      recurrence = new_recurrence(options)
+
+      identical_recurrence = new_recurrence(options)
+      different_recurrence = new_recurrence(options.merge(interval: 2))
+
+      _(recurrence).must_equal identical_recurrence
+      _(recurrence).wont_equal different_recurrence
+    end
+  end
+
   describe ".dump" do
     it "returns options as JSON string" do
       options = {every: :day, total: 3, starts: now, interval: 1}