Fix imbalanced horizontal spacing.

In order to make the horizontal spacing balancing with the original
trailing whitespaces, we now determine the default horizontal
spacing by using the whitespace character ' '.
Use Core Text attributes instead of Cocoa's.

Even though they are identical (at least on OS X 10.8),
since the documentation does not state this,
we prefer the Core Text attributes.
Fix the additional pixel in the background.

The additional line with 1 pixel of height that sometimes
appears is due to the fraction part in the rects.
This issue has been fixed, the fraction parts in calculated
origins and sizes are all removed by using round/floor/ceil.
Fix uneven line spacing in vertical layout.
Revert "Revert "Merge pull request #15 from lembacon/master""

This reverts commit ce4f21fdb9e26e241c70bbb1c4411610654ad4d9.
Merge branch 'master' of https://github.com/lembacon/squirrel into core_text
Fix abnormal font leading metric caused by U+30FB.

Fixed the abnormally large scaled font leading metric
caused by Japanese character U+30FB by specifying a
maximum font leading metric in order to restrict
the maximum line height.

(See https://github.com/lotem/squirrel/pull/15#issuecomment-12600211
 for more information.)
Revert "Remove trailing whitespace in candidate format."

I believe that an extra space looks better for most of us and qualify
the default, a conclusion based on user feedback.

This reverts commit ebc5414db8ec7410b160224b1306a62221da1727.
squirrel.yaml: bump version.