Allow rewriting path of modules in define.

This PR adds the ability to rewrite the path of a module. The rewrites are passed as options to the deamdify transform.

Example:
```
// package.json
{
  ...
  "browserify": {
    "transform": [
      ["deamdify", {
        "rewrites": {
          "uri": "URIjs/src"
        }
      }]
    ]
  }
}
```

This will transform:

```
define(["uri/URI"], function(URI) {
  ...
})
```
to
```
var URI = require("URIjs/src/URI");
...
```

This relates to #14 .