Migrate all crates to the 2018 edition

Most of the CLI crates were already in the 2018 edition, and it turns
out that one of the macro crates was already in the 2018 edition so we
may as well move everything to the 2018 edition!

Always nice to remove those `extern crate` statements nowadays!

This commit also does a `cargo fmt --all` to make sure we're conforming
with style again.

crates/typescript-tests/src/custom_section.rs

@@ -8,4 +8,4 @@ const TS_INTERFACE_EXPORT: &'static str = r"
 #[wasm_bindgen]
 pub struct Person {
     pub height: u32,
-}
+}

crates/typescript-tests/src/lib.rs

@@ -1,4 +1,4 @@
 mod custom_section;
 mod opt_args_and_ret;
 mod simple_fn;
-mod simple_struct;
+mod simple_struct;

crates/typescript-tests/src/opt_args_and_ret.rs

@@ -3,4 +3,4 @@ use wasm_bindgen::prelude::*;
 #[wasm_bindgen]
 pub fn opt_fn(_a: Option<i32>) -> Option<i32> {
     None
-}
+}

crates/typescript-tests/src/simple_fn.rs

@@ -1,4 +1,4 @@
 use wasm_bindgen::prelude::*;
 
 #[wasm_bindgen]
-pub fn greet(_: &str) {}
+pub fn greet(_: &str) {}

crates/typescript-tests/src/simple_struct.rs

@@ -1,12 +1,11 @@
 use wasm_bindgen::prelude::*;
 
 #[wasm_bindgen]
-pub struct A {
-}
+pub struct A {}
 
 #[wasm_bindgen]
 impl A {
-    #[wasm_bindgen(constructor)]    
+    #[wasm_bindgen(constructor)]
     pub fn new() -> A {
         A {}
     }
@@ -14,4 +13,4 @@ impl A {
     pub fn other() {}
 
     pub fn foo(&self) {}
-}
+}