Update all dependencies

Because of a breaking change in babel-preset-env, we needed to change the
way the targets options are set. It used to be that you could just set one
to false to have it not be included, but now the key mustn't be there on
the targets object at all.

package.json

@@ -7,47 +7,47 @@
   "version": "0.7.3",
   "description": "The Zambezi build process",
   "devDependencies": {
-    "babel-cli": "6.23.0",
-    "babel-plugin-istanbul": "4.0.0",
-    "babel-register": "6.23.0",
+    "babel-cli": "6.26.0",
+    "babel-plugin-istanbul": "4.1.5",
+    "babel-register": "6.26.0",
     "bats": "0.4.2",
-    "codecov": "1.0.1",
+    "codecov": "3.0.0",
     "deep-equal": "1.0.1",
-    "depcheck": "0.6.7",
-    "js-combinatorics": "0.5.2",
-    "nyc": "10.1.2",
-    "tape": "4.6.3",
-    "tape-async": "2.1.1"
+    "depcheck": "0.6.8",
+    "js-combinatorics": "0.5.3",
+    "nyc": "11.3.0",
+    "tape": "4.8.0",
+    "tape-async": "2.3.0"
   },
   "dependencies": {
     "@zambezi/babel-plugin-transform-es2015-modules-umd": "^6.18.2",
     "ansicolors": "0.3.2",
     "babel-core": "^6.23.1",
     "babel-plugin-add-module-exports": "^0.2.1",
     "babel-polyfill": "^6.23.0",
-    "babel-preset-env": "1.1.8",
+    "babel-preset-env": "1.6.1",
     "babel-preset-react": "^6.23.0",
     "babel-preset-stage-0": "^6.22.0",
     "babel-preset-stage-1": "^6.22.0",
     "babel-preset-stage-2": "^6.22.0",
     "babel-preset-stage-3": "^6.22.0",
-    "chokidar": "1.6.1",
-    "commander": "2.9.0",
+    "chokidar": "1.7.0",
+    "commander": "2.12.2",
     "funkis": "0.2.0",
-    "glob": "7.1.1",
+    "glob": "7.1.2",
     "mkdirp": "0.5.1",
-    "pino": "4.0.0",
-    "pkginfo": "0.4.0",
-    "postcss": "^5.2.14",
-    "postcss-cssnext": "^2.9.0",
-    "postcss-import": "^9.1.0",
-    "postcss-url": "^6.3.1",
-    "read-package-json": "2.0.4",
-    "source-map-support": "0.4.11",
-    "strip-ansi": "3.0.1",
-    "thenify": "3.2.1",
-    "window-size": "0.3.0",
-    "write-file-atomic": "1.3.1"
+    "pino": "4.10.2",
+    "pkginfo": "0.4.1",
+    "postcss": "^6.0.14",
+    "postcss-cssnext": "^3.0.2",
+    "postcss-import": "^11.0.0",
+    "postcss-url": "^7.3.0",
+    "read-package-json": "2.0.12",
+    "source-map-support": "0.5.0",
+    "strip-ansi": "4.0.0",
+    "thenify": "3.3.0",
+    "window-size": "1.1.0",
+    "write-file-atomic": "2.3.0"
   },
   "scripts": {
     "build": "babel src -d lib --source-maps",

src/builder/javascript.js

@@ -21,8 +21,6 @@ export default function configure(pkg, opts) {
       , ['es-stage']: stage
       } = opts.flags
 
-  let targets = opts.targets
-
   if (modules === 'ecmascript') {
     modules = false
     addModuleExports = false
@@ -41,14 +39,16 @@ export default function configure(pkg, opts) {
     }
   }
 
+  let targets = {}
+
+  opts.targetNode && (targets.node = opts.targetNode)
+  opts.targetBrowsers && (targets.browsers = opts.targetBrowsers)
+
   presets.push(
     preset_env(null,
       { debug: !!global.process.env.DEBUG
       , modules
-      , targets:
-        { node: opts.targetNode
-        , browsers: opts.targetBrowsers
-        }
+      , targets
       , exclude: ['transform-es2015-modules-umd']
       , useBuiltIns: true
       }