Clean up target arch support based on pull request electron-userland#55…

… comments.

README.md

@@ -39,6 +39,11 @@ electron
 
 If you need to use an HTTP proxy you can [set these environment variables](https://github.com/request/request/tree/f0c4ec061141051988d1216c24936ad2e7d5c45d#controlling-proxy-behaviour-using-environment-variables)
 
+If you want to change the architecture that is downloaded (e.g., `ia32` on an `x64` machine), you can use the `--arch` flag with npm install or set the `npm_config_arch` environment variable:
+```
+npm install --arch=ia32 electron-prebuilt
+```
+
 ## About
 
 Works on Mac, Windows and Linux OSes that Electron supports (e.g. Electron [does not support Windows XP](https://github.com/atom/electron/issues/691)).

install.js

@@ -23,11 +23,8 @@ var paths = {
 
 if (!paths[platform]) throw new Error('Unknown platform: ' + platform)
 
-if (process.env.npm_config_arch) {
-    download({version: version, arch: process.env.npm_config_arch}, extractFile)
-} else {
-    download({version: version}, extractFile)
-}
+// downloads if not cached
+download({version: version, arch: process.env.npm_config_arch}, extractFile)
 
 // unzips and makes path.txt point at the correct executable
 function extractFile (err, zipPath) {