Added livescript.js compile support add Generated by LiveScript header. ...

LiveScript compile now support add Generated by LiveScript [VERSION] header to compiled files. 

Default is ENABLED.

This behavior can be disabled by options with compile key to false.
Example: 
```
options = {compile: false, bare: true};
var output = require('LiveScript').compile(code, options);
```

fixed #359

Signed-off-by: Rack Lin <racklin@gmail.com>