Move CLI crate to root of workspace

Somehow I missed that this was a thing you could do? It's a much
cleaner organization, and it makes it so that you don't have to
explicitly specify the crate to build.

schema/build.rs

@@ -1,6 +1,6 @@
 fn main() {
     cynic_codegen::register_schema("startgg")
-        .from_sdl_file("src/startgg.graphql")
+        .from_sdl_file("startgg.graphql")
         .unwrap()
         .as_default()
         .unwrap();