Remove deprecated options from README.md.

Author: benjamn

README.md

@@ -30,22 +30,21 @@ var install = require("install").makeInstaller({
   // identifiers if they do not exactly match an installed module.
   extensions: [".js", ".json"],
 
-  // If defined, the options.onInstall function will be called any time
-  // new modules are installed.
-  onInstall,
-
-  // If defined, the options.override function will be called before
-  // looking up any top-level package identifiers in node_modules
-  // directories. It can return either a string to provide an alternate
-  // package identifier or a non-string value to prevent the lookup from
-  // proceeding.
-  override,
-
   // If defined, the options.fallback function will be called when no
   // installed module is found for a required module identifier. Often
   // options.fallback will be implemented in terms of the native Node
   // require function, which has the ability to load binary modules.
-  fallback
+  fallback,
+
+  // Boolean flag indicating whether the installed code will be running in
+  // a web browser.
+  browser,
+
+  // List of fields to look for in package.json files to determine the
+  // main entry module of the package. The first field listed here whose
+  // value is a string will be used to resolve the entry module. Defaults
+  // to just ["main"], or ["browser", "main"] if options.browser is true.
+  mainFields: ["browser", "main"],
 });
 ```