Improve clarity of shorthand linter through naming

This commit improves the clarity of the shorthand linter by assigning
the values of the array that contains a property's shorthand values to
named variables that correspond to their placement (top, right, bottom,
and left).

Related Story:
  http://www.pivotaltracker.com/story/show/43148129
  ("Teach scss-lint about missed shorthand case")

Change-Id: Idc8833d36f2857eb56f7bada40674d5ba88ead14
Reviewed-on: https://gerrit.causes.com/17754
Reviewed-by: Lann Martin <lann@causes.com>
Tested-by: Joe Lencioni <joe.lencioni@causes.com>
Bump version to 0.5

Related Story:
  http://www.pivotaltracker.com/story/show/43148129
  ("Teach scss-lint about missed shorthand case")

Change-Id: I8b724a7b3cfe62894b65e3294c5fa1fe40c933eb
Reviewed-on: https://gerrit.causes.com/17750
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Tested-by: Joe Lencioni <joe.lencioni@causes.com>