docs; make gm().command() public

README.md

@@ -164,12 +164,13 @@ gm('img.jpg')
 
 If `gm` does not supply you with a method you need or does not work as you'd like, you can simply use `gm().in()` or `gm().out()` to set your own arguments.
 
+- `gm().command()` - Custom command such as `identify` or `convert`
 - `gm().in()` - Custom input arguments
 - `gm().out()` - Custom output arguments
 
 The command will be formatted in the following order:
 
-1. `command` - ie `gm convert` or `convert`
+1. `command` - ie `convert`
 2. `in` - the input arguments
 3. `source` - stdin or an image file
 4. `out` - the output arguments
@@ -215,6 +216,10 @@ First download and install [GraphicsMagick](http://www.graphicsmagick.org/) or [
     brew install imagemagick
     brew install graphicsmagick
 
+If you want WebP support with ImageMagick, you must add the WebP option:
+
+    brew install imagemagick --with-webp
+
 then either use npm:
 
     npm install gm

lib/args.js

@@ -12,7 +12,7 @@ var argsToArray = require('./utils').argsToArray;
 module.exports = function (proto) {
 
   // define the sub-command to use, http://www.graphicsmagick.org/utilities.html
-  proto.subCommand = function subCommand (name){
+  proto.command = proto.subCommand = function subCommand (name){
     this._subCommand = name;
     return this;
   }