add emitting of integer and float literals

- remove panics
 - add emitting for return statements
 - remove default emitting of return a+b;

examples/hello.ry

@@ -1,7 +1,7 @@
 // import std;
 
-fn add(a: i32, b: i32) i32 {
-    return a + b;
+fn add() i32 {
+    return 1 + 1;
 }
 
 // type is void by default