fix(create-key): use browser MSR-JavaScript-Crypto polyfill

It works, but the tests are really slow.

.editorconfig

@@ -0,0 +1,13 @@
+# EditorConfig from https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# All files
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true

lib/create-key.js

@@ -1,29 +1,56 @@
 'use strict'
 
 var Buffer = require('buffer/').Buffer
-var pbkdf2 = require('pbkdf2')
-var Promise = require('lie')
 var randomBytes = require('randombytes')
+var subtle = (global.crypto && global.crypto.subtle) ||
+  (global.msCrypto && window.msCrypto.subtle) ||
+  (global.msrCrypto && window.msrCrypto.subtle) ||
+  require('./helpers/msrcrypto').subtle
 
 module.exports = function createKey (password, saltArg) {
-  var digest = 'sha256'
+  var passwordBuffer = toBuffer(password, 'utf-8', 'password')
+  var digest = 'SHA-256'
   var iterations = 100000
+  var keyLength = 256 / 8
+
   var salt = saltArg != null && typeof saltArg === 'string' && saltArg.length === 32
     ? saltArg
     : randomBytes(16).toString('hex')
+  var saltyBuffy = Buffer.from(salt, 'hex')
+
+  return subtle.importKey('raw', passwordBuffer, { name: 'PBKDF2' }, false, ['deriveBits'])
 
-  return new Promise(function (resolve, reject) {
-    var saltyBuffy = Buffer.from(salt, 'hex')
+    .then(function (key) {
+      return subtle.deriveBits(
+        {
+          name: 'PBKDF2',
+          salt: saltyBuffy,
+          iterations: iterations,
+          hash: {
+            name: digest
+          }
+        },
+        key,
+        keyLength << 3
+      )
+    })
 
-    pbkdf2.pbkdf2(password, saltyBuffy, iterations, 256 / 8, digest, function (err, key) {
-      if (err) {
-        reject(err)
-      } else {
-        resolve({
-          key: key,
-          salt: salt
-        })
+    .then(function (res) {
+      return {
+        key: Buffer.from(res),
+        salt: salt
       }
     })
-  })
+}
+
+function toBuffer (thing, encoding, name) {
+  if (Buffer.isBuffer(thing)) {
+    return thing
+  } else if (typeof thing === 'string') {
+    return Buffer.from(thing, encoding)
+  } else if (ArrayBuffer.isView(thing)) {
+    return Buffer.from(thing.buffer)
+  } else {
+    throw new TypeError(name + ' must be a string, a Buffer, a typed array or a DataView')
+  }
 }