Speed up Travis by running Webpack in fewer tests (#381)

* Reorganize Travis configuration

* Add a `JOB` env var descriptor to all matrix entries. Not used anywhere but is
  useful when viewing the whole build on Travis's web interface.
* Reorganize where builds are located, moving slow builds first and fast ones
  last.
* Change checking the CLI builds from `cargo build` to `cargo check`
* Use YAML references to reduce some duplication

* Print some more timing statistics for each test

* Extract `Project` helper in tests to a module

This'll help make it a bit more extensible over time. At the same time the
methods are also slightly reorganized to read more clearly from top to bottom.

* Migrate all tests away from Webpack

Wepback can take a significant amount of time to execute and when it's
multiplied by hundreds of tests that adds up really quickly! After investigating
Node's `--experimental-modules` option it looks like it's suitable for our use
so this switches all tests to using JS files (moving away from TypeScript as
well) with `--experimental-modules` with Node.

Tests will be selectively re-enabled with webpack and node.js specific output
(that doesn't require `--experimental-modules`), coming in later commits.

* Restore the node test for node.js output

Ensures it's workable as-is

* Only generate typescript with webpack

* Only read wasm files for webpack

* Skip package.json/node_modules for now

* Only generate webpack config if needed

* Start a dedicated test module for typescript

Will hopefully verify the generated Typescript compiles OK.

* Remove unneeded `node` method

* Fixup some rebase conflicts

* Don't run asmjs example on travis

* Fixup generator tests

* Attempt to fix windows

* Comment windows fix

* More test fixes

* More exclusions

* More test fixes

* Relax eslint regex

Catch mjs modules as well

* Fix eslint

* Speed up travis on examples slightly

crates/cli-support/src/js/mod.rs

@@ -60,7 +60,7 @@ impl<'a> Context<'a> {
         if let Some(ref c) = comments {
             self.globals.push_str(c);
         }
-        let global = if self.config.nodejs {
+        let global = if self.use_node_require() {
             if contents.starts_with("class") {
                 format!("{1}\nmodule.exports.{0} = {0};\n", name, contents)
             } else {
@@ -412,12 +412,12 @@ impl<'a> Context<'a> {
         } else {
             let import_wasm = if self.globals.len() == 0 {
                 String::new()
-            } else if self.config.nodejs {
+            } else if self.use_node_require() {
                 self.footer
                     .push_str(&format!("wasm = require('./{}_bg');", module_name));
                 format!("var wasm;")
             } else {
-                format!("import * as wasm from './{}_bg.wasm';", module_name)
+                format!("import * as wasm from './{}_bg';", module_name)
             };
 
             format!(
@@ -977,7 +977,9 @@ impl<'a> Context<'a> {
         if !self.exposed_globals.insert("text_encoder") {
             return;
         }
-        if self.config.nodejs {
+        if self.config.nodejs_experimental_modules {
+            self.imports.push_str("import { TextEncoder } from 'util';\n");
+        } else if self.config.nodejs {
             self.global(
                 "
                 const TextEncoder = require('util').TextEncoder;
@@ -1003,7 +1005,9 @@ impl<'a> Context<'a> {
         if !self.exposed_globals.insert("text_decoder") {
             return;
         }
-        if self.config.nodejs {
+        if self.config.nodejs_experimental_modules {
+            self.imports.push_str("import { TextDecoder } from 'util';\n");
+        } else if self.config.nodejs {
             self.global(
                 "
                 const TextDecoder = require('util').TextDecoder;
@@ -1585,6 +1589,10 @@ impl<'a> Context<'a> {
         *section.payload_mut() = contents.into_bytes();
         self.module.sections_mut().push(Section::Custom(section));
     }
+
+    fn use_node_require(&self) -> bool {
+        self.config.nodejs && !self.config.nodejs_experimental_modules
+    }
 }
 
 impl<'a, 'b> SubContext<'a, 'b> {
@@ -1944,7 +1952,7 @@ impl<'a, 'b> SubContext<'a, 'b> {
             let name = import.js_namespace.as_ref().map(|s| &**s).unwrap_or(item);
 
             if self.cx.imported_names.insert(name.to_string()) {
-                if self.cx.config.nodejs {
+                if self.cx.use_node_require() {
                     self.cx.imports.push_str(&format!(
                         "\
                          const {} = require('{}').{};\n\