Added alias feature

[tandrewnichols]

Adds an alias feature:

program
  .command('remove <target>')
  .alias('rm')
  .description('Remove target <target>')
  .action(function() {
    /* Take action */
  });

Also cleans up commandHelp a little. At least for me, it never looks pretty because

command [options] <arg>

is almost always longer than the given 22 space padding, so each command lines up differently. Plus, with adding an alias, it gets even longer. This just breaks the description onto a separate line, with a bit of padding at the front (and adds a newline after each command).

[davidglivar]

+1

[mattma]

This is nice, why it did not get merged?

[SomeKittens]

@mattma Commander.js is under new management, so things are still a bit shaky. Great PR, but there are conflicts with the current version. Bring it up to date and I'll merge it in.

[tandrewnichols]

Do you prefer this interface or the one in #64? I'm happy to update if this will actually be used.

[SomeKittens]

@tandrewnichols I like this one better - the syntax is a little clearer. I'll close the other one. Thanks!

[SomeKittens]

@tandrewnichols Thanks!