Windows Portable App (#417)

* packager: call callbacks consistently

Before this, the callbacks would not being called, which would lead to
an incomplete build on non-OS X platforms when trying to build all for
all platforms.

* packager: Always produce OS X update file regardless of --package option

This makes it consistent with how the windows build always produces the
.nupkg autoupdate files

* packager: fix duplicate npm install

Move "npm prune && npm dedupe" into the release script. Remove an extra
"npm install"

* Make Windows portable app

When a folder named "Portable Settings" exists in same folder as
WebTorrent.exe, then use it instead of the default application config
path.

Closes #358

* packager: remove redundant signing warning

* cross platform zip function

* Set config file path to match config.CONFIG_PATH

* portable app: make electron settings portable

* portable: fix poster/torrent paths

* use cross-zip

* portable app: default download folder inside 'Portable Settings'

package.json

@@ -15,8 +15,7 @@
   },
   "dependencies": {
     "airplay-js": "guerrerocarlos/node-airplay-js",
-    "application-config": "^0.2.0",
-    "application-config-path": "^0.1.0",
+    "application-config": "feross/node-application-config",
     "bitfield": "^1.0.2",
     "chromecasts": "^1.8.0",
     "concat-stream": "^1.5.1",
@@ -43,6 +42,7 @@
     "winreg": "^1.1.1"
   },
   "devDependencies": {
+    "cross-zip": "^1.0.0",
     "electron-osx-sign": "^0.3.0",
     "electron-packager": "^6.0.2",
     "electron-winstaller": "feross/windows-installer#build",
@@ -50,6 +50,7 @@
     "minimist": "^1.2.0",
     "nobin-debian-installer": "^0.0.9",
     "plist": "^1.2.0",
+    "run-series": "^1.1.4",
     "standard": "^6.0.5"
   },
   "homepage": "https://webtorrent.io",
@@ -71,7 +72,7 @@
   },
   "scripts": {
     "clean": "node ./bin/clean.js",
-    "package": "npm install && npm prune && npm dedupe && node ./bin/package.js",
+    "package": "node ./bin/package.js",
     "start": "electron .",
     "test": "standard",
     "update-authors": "./bin/update-authors.sh"