Refactored parseAttrs

Moved parseAttrs from GlusterFileChannel to GlusterFileAttributes. Made it a static method to enable its use in GFChannel. Modified the unit tests for GFAttributes and GFChannel to reflect this refactoring.
Please change this to not call contains(). Instead, just call get() and check for a null value. Also, move to top with other static stuff. I think this should be the last of the static methods at the top of the file.