Created a custom sass importer for sassyjson

First try to solve issue #42 

I have no idea what I am doing here. Never wrote any ruby before...

Have to resolve the path issue. Path have to be relative to the first scss file. 

How dose it work? 

This:
```scss
@import "SassyJSON";
@import "test.json"; 
```
is equal to this:
```scss
@import "SassyJSON";
$test : json_decode('[file content]');
```