Move class intialization to method

This allows generating the init function from class names alone

src/coercions/mod.rs

@@ -49,3 +49,7 @@ pub type ToRubyResult = Result<VALUE, Error>;
 pub trait ToRuby {
     fn to_ruby(self) -> ToRubyResult;
 }
+
+pub trait InitRuby {
+    fn init_ruby();
+}

src/macros/codegen.rs

@@ -212,10 +212,44 @@ macro_rules! codegen_method {
     };
 }
 
+#[macro_export]
+macro_rules! codegen_ruby_init {
+    ({
+        type: class,
+        rust_name: $rust_name:tt,
+        ruby_name: $ruby_name:tt,
+        meta: { pub: $pub:tt, reopen: $reopen:tt },
+        struct: (),
+        methods: $methods:tt
+    }) => (
+        impl $crate::InitRuby for $rust_name {
+            fn init_ruby() {
+                codegen_class_binding!({
+                    type: class,
+                    rust_name: $rust_name,
+                    ruby_name: $ruby_name,
+                    meta: { pub: $pub, reopen: $reopen },
+                    struct: (),
+                    methods: $methods
+                }, {
+                    type: class,
+                    rust_name: $rust_name,
+                    ruby_name: $ruby_name,
+                    meta: { pub: $pub, reopen: $reopen },
+                    struct: (),
+                    methods: $methods
+                });
+            }
+        }
+    );
+}
+
+
 #[macro_export]
 macro_rules! codegen_extra_impls {
     ($class:tt) => (
         codegen_allocator!($class);
         codegen_coercions!($class);
+        codegen_ruby_init!($class);
     )
 }

src/macros/init.rs

@@ -1,18 +1,32 @@
 #[macro_export]
 macro_rules! codegen_init {
-    { [ $($class:tt)* ] } => {
+    // Extracts the list of rust class names and calls the actual codegen_init with that
+    { [ $({
+        type: class,
+        rust_name: $ rust_name: tt,
+        ruby_name: { $ ( $ ruby_name: tt) * },
+        meta: { pub: $ pub: tt, reopen: false },
+        struct: (),
+        methods: [ $ ( $ method: tt) * ]
+    })* ] } => (
+        codegen_init!{ [ $($rust_name)* ] }
+    );
+
+    { [ $($rust_name:tt)* ] } => {
         #[allow(non_snake_case)]
         #[no_mangle]
         pub extern "C" fn Init_native() {
+            use $crate::InitRuby;
             $crate::sys::check_version();
 
             $(
-                codegen_class_binding!($class, $class);
+                $rust_name::init_ruby();
             )*
         }
-    }
+    };
 }
 
+
 #[macro_export]
 macro_rules! codegen_class_binding {
     { $class:tt, {