cargo fuzz integration (#306)

* added wip translate_module fuzzer

* use local binaryen-rs fork (with shim) for fuzzing

* minor doc cleanup

* check fuzzer integration via CI

* switch back to upstream binaryen-rs; add forgotten integration test directive

cranelift/fuzz/fuzz_translate_module.rs

@@ -0,0 +1,15 @@
+#![no_main]
+#[macro_use]
+extern crate libfuzzer_sys;
+extern crate binaryen;
+extern crate cretonne_wasm;
+use cretonne_wasm::{translate_module, DummyEnvironment};
+
+fuzz_target!(|data: &[u8]| {
+    let binaryen_module = binaryen::tools::translate_to_fuzz_mvp(data);
+
+    let wasm = binaryen_module.write();
+
+    let mut dummy_environ = DummyEnvironment::default();
+    translate_module(&wasm, &mut dummy_environ).unwrap();
+});