Close #974 Better 'doing it wrong' output for 'npm version'

lib/version.js

@@ -12,13 +12,15 @@ var exec = require("./utils/exec")
   , npm = require("../npm")
 
 version.usage = "npm version <newversion>\n(run in package dir)\n"
-              + "'npm -v' or 'npm --version' to print npm version\n"
-              + "(which is "+npm.version+")"
+              + "'npm -v' or 'npm --version' to print npm version "
+              + "("+npm.version+")\n"
+              + "'npm view <pkg> version' to view a package's "
+              + "published version"
 
 function version (args, cb) {
   if (args.length !== 1) return cb(version.usage)
   var newVer = semver.valid(args[0])
-  if (!newVer) return cb(new Error("invalid version: "+args[0]))
+  if (!newVer) return cb(version.usage)
   readJson(path.join(process.cwd(), "package.json"), function (er, data) {
     if (er) return log.er(cb, "No package.json found")(er)
     if (data.version === newVer) return cb(new Error("Version not changed"))