Support for unified Integer class in Ruby 2.4+

Ruby 2.4 unifies Fixnum and Bignum into Integer: https://bugs.ruby-lang.org/issues/12005

lib/v8/conversion.rb

@@ -18,7 +18,7 @@ for type in [TrueClass, FalseClass, NilClass, Float] do
   end
 end
 
-for type in [Class, Object, Array, Hash, String, Symbol, Time, Proc, Method, Fixnum] do
+for type in [Class, Object, Array, Hash, String, Symbol, Time, Proc, Method, Integer] do
   type.class_eval do
     include V8::Conversion.const_get(type.name)
   end

lib/v8/conversion/fixnum.rb

@@ -1,5 +1,5 @@
 class V8::Conversion
-  module Fixnum
+  module Integer
     def to_ruby
       self
     end

spec/v8/conversion_spec.rb

@@ -21,30 +21,30 @@ describe V8::Conversion do
     klass.test.should be_instance_of(::Set)
   end
 
-  context "::Fixnum" do
+  context "::Integer" do
     context "for 32-bit numbers" do
       it "should convert positive integer" do
-        cxt['fixnum_a'] = 123
-        cxt['fixnum_a'].should == 123
-        cxt['fixnum_a'].should be_instance_of(Fixnum)
+        cxt['integer_a'] = 123
+        cxt['integer_a'].should == 123
+        cxt['integer_a'].should be_kind_of(Integer)
       end
 
       it "should convert negative integer" do
-        cxt['fixnum_b'] = -123
-        cxt['fixnum_b'].should == -123
-        cxt['fixnum_b'].should be_instance_of(Fixnum)
+        cxt['integer_b'] = -123
+        cxt['integer_b'].should == -123
+        cxt['integer_b'].should be_kind_of(Integer)
       end
     end
 
     context "for 64-bit numbers" do
       it "should convert positive integer" do
-        cxt['fixnum_c'] = 0x100000000
-        cxt['fixnum_c'].should == 0x100000000
+        cxt['integer_c'] = 0x100000000
+        cxt['integer_c'].should == 0x100000000
       end
 
       it "should convert negative integer" do
-        cxt['fixnum_d'] = -0x100000000
-        cxt['fixnum_d'].should == -0x100000000
+        cxt['integer_d'] = -0x100000000
+        cxt['integer_d'].should == -0x100000000
       end
     end