Add spec to exercise numeric Enum deserialization

spec/database_spec.cr

@@ -8,7 +8,7 @@ describe DB::Database do
 
       db.setup_connection do |cnn|
         cnn_setup += 1
-        cnn.scalar("1").should eq "1"
+        cnn.scalar("a").should eq "a"
       end
 
       cnn_setup.should eq(2)

spec/dummy_driver.cr

@@ -187,7 +187,7 @@ class DummyDriver < DB::Driver
         return (@statement.as(DummyStatement)).params[0]
       end
 
-      return n
+      n.to_i64? || n
     end
 
     def next_column_index : Int32

spec/serializable_spec.cr

@@ -90,10 +90,10 @@ struct ModelWithEnum
   getter c2 : MyOtherEnum
 
   enum MyEnum
-    Foo
-    Bar
-    Baz
-    Quux
+    Foo  = 0
+    Bar  = 1
+    Baz  = 2
+    Quux = 3
   end
 
   enum MyOtherEnum
@@ -196,7 +196,7 @@ describe "DB::Serializable" do
   end
 
   it "should initialize a model with an enum property" do
-    expect_model("1,Baz,LOL", ModelWithEnum, {
+    expect_model("1,2,LOL", ModelWithEnum, {
       c0: 1,
       c1: ModelWithEnum::MyEnum::Baz,
       c2: ModelWithEnum::MyOtherEnum::LOL,