Named Routes

Giving routes names or aliases makes them easier to reference while generating links. Also since your link generation is no longer complete dependent on defining default path variables.

```php
<?php

include 'Net/URL/Mapper.php';

$m = Net_URL_Mapper::getInstance();
$m->connect('articles/category/:id', array('controller'=>'articles', 'action'=>'category'), 'article_category');

// With Named Routes
$m->generateFromAlias('article_category', array('id' => 'bingo'));

// Without Named Routes
$m->generate(array('controller'=>'articles', 'action'=>'category', 'id' => 'bingo'));
```

To give routes named I created a new generate function, generateFromAlias. It is a lot like the first one, though instead of matching routes purely based off the default variables, it now matches based off the alias.  I updated connect to except a 4th article the alias. I then used the existing Path::setAlias and Path::getAlias functionality.  This change is 100% backwards compatible.
I also made a change in the Mapper::generate function instead of doing two counts I set a [boolean flag](https://github.com/baileylo/Net_URL_Mapper/commit/45732fc45c44023468daf11a0baa7c1c2b316b39#L0R277).