Fix help section order and padding (#652)

* Change help section order

Fixes #500

Previous display order :

Usage > Commands > Description > Options

New display order:

Usage > Description > Options > Commands

* Fix inconsistent padding between help sections

examples/pm

@@ -4,6 +4,7 @@ var program = require('..');
 
 program
   .version('0.0.1')
+  .description('Fake package manager')
   .command('install [name]', 'install one or more packages').alias('i')
   .command('search [query]', 'search with optional query').alias('s')
   .command('list', 'list packages installed')

index.js

@@ -1021,17 +1021,17 @@ Command.prototype.helpInformation = function() {
   if (commandHelp) cmds = [commandHelp];
 
   var options = [
-    '  Options:'
+    ''
+    , '  Options:'
     , ''
     , '' + this.optionHelp().replace(/^/gm, '    ')
     , ''
-    , ''
   ];
 
   return usage
-    .concat(cmds)
     .concat(desc)
     .concat(options)
+    .concat(cmds)
     .join('\n');
 };