Refactor

I've done some refactoring. You can get it in your project if you want.

New Features
- the lessphp dependency is now managed with composer
- The lessphp nows generate unique files if useOneFile is false and true
- There is a cache strategy with lessphp method, if the .less source file hasn't changed the css destination file isn't regenerated

Warnings
- I didn't have the courage to code the lessc method (as it seemed very similar to lessphp method it shouldn't be very long)

For those who whants there's still some work to do (see FIXME and TODO comments in ezless.php)