add cli support for --transform-key to support mode's like production…

…/staging/etc..

bin/advanced.txt

@@ -56,6 +56,15 @@ Advanced Options:
     Turn off package.json browser field resolution. This is also handy if you
     need to run a bundle in node.
 
+  --transform-key
+
+    Instead of the default package.json#browserify#transform field to list
+    all transforms to apply when running browserify, a custom field, like, e.g.
+    package.json#browserify#production or package.json#browserify#staging
+    can be used, by for example running:
+    * `browserify index.js --transform-key=production > bundle.js`
+    * `browserify index.js --transform-key=staging > bundle.js`
+
   --node
 
     Alias for --bare and --no-browser-field.

bin/args.js

@@ -105,6 +105,7 @@ module.exports = function (args, opts) {
         bundleExternal: argv['bundle-external'],
         basedir: argv.basedir,
         browserField: argv.browserField,
+        transformKey: argv['transform-key'] ? ['browserify', argv['transform-key']] : undefined,
         dedupe: argv['dedupe'],
 
         detectGlobals: argv.detectGlobals,

readme.markdown

@@ -164,6 +164,15 @@ Advanced Options:
     Turn off package.json browser field resolution. This is also handy if you
     need to run a bundle in node.
 
+  --transform-key
+
+    Instead of the default package.json#browserify#transform field to list
+    all transforms to apply when running browserify, a custom field, like, e.g.
+    package.json#browserify#production or package.json#browserify#staging
+    can be used, by for example running:
+    * `browserify index.js --transform-key=production > bundle.js`
+    * `browserify index.js --transform-key=staging > bundle.js`
+
   --node
 
     Alias for --bare and --no-browser-field.