Cleanup documentation of Exception,File and Parser

Add documentation, change variable namens and use functions instead of
magic calls (performance)
More cleanups

Documentation change include to require, remove magic property access
and use getter functions
Fix regression

Fix regression
Introduce a SassLoader as Autoloader

Create a basic autoloader to load the classes. There is still a
workaround, because the classes are not PSR compatible, if this request
is merged I start to move classes to get a clean and performant
Sassparser
Merge pull request #157 from lochmueller/cleanup

Cleanup & Autoloader