fix(json): Fix jsonification for Ruby < 2.4

lib/jekyll/algolia/utils.rb

@@ -104,6 +104,12 @@ module Jekyll
           Integer, Float,
           String
         ]
+        # Integer arrived in Ruby 2.4. Before that it was Fixnum and Bignum
+        if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.4.0')
+          # rubocop:disable Lint/UnifiedInteger
+          simple_types += [Fixnum, Bignum]
+          # rubocop:enable Lint/UnifiedInteger
+        end
         return item if simple_types.member?(item.class)
 
         # Recursive types

spec/jekyll/algolia/utils_spec.rb

@@ -161,7 +161,7 @@ describe(Jekyll::Algolia::Utils) do
       let(:item) { 'foo' }
       it { should eq 'foo' }
     end
-    context 'with a number' do
+    context 'with an integer' do
       let(:item) { 42 }
       it { should eq 42 }
     end
@@ -169,6 +169,10 @@ describe(Jekyll::Algolia::Utils) do
       let(:item) { 42.42 }
       it { should eq 42.42 }
     end
+    context 'with a large number' do
+      let(:item) { 2**62 }
+      it { should eq 2**62 }
+    end
     context 'with a boolean (true)' do
       let(:item) { true }
       it { should eq true }