fix examples

wasmtime-api/examples/gcd.rs

@@ -1,11 +1,11 @@
-use failure::Error;
+use failure::{format_err, Error};
 use std::cell::RefCell;
 use std::fs::read;
 use std::rc::Rc;
-use wasm_rust_api::*;
+use wasmtime_api::*;
 
 fn main() -> Result<(), Error> {
-    let wasm = read("gcd.wasm")?;
+    let wasm = read("examples/gcd.wasm")?;
     let engine = Rc::new(RefCell::new(Engine::default()));
     let store = Rc::new(RefCell::new(Store::new(engine)));
     let module = Rc::new(RefCell::new(Module::new(store.clone(), &wasm)?));
@@ -22,7 +22,10 @@ fn main() -> Result<(), Error> {
         .borrow()
         .func()
         .clone();
-    let result = gcd.borrow().call(&[Val::from(6i32), Val::from(27i32)])?;
+    let result = gcd
+        .borrow()
+        .call(&[Val::from(6i32), Val::from(27i32)])
+        .map_err(|e| format_err!("call error: {:?}", e))?;
     println!("{:?}", result);
     Ok(())
 }