Fix SpaceBeforeBrace bug for single line blocks

This fixes issue #94 where `scss-lint` didn't report lints for single
line blocks such as:

  .single-line-selector{color: #fff;}

The solution was to remove the requirement that `{` was the last
character in the line.

Change-Id: I365333ff8f0a34580b3649f8d6c25c732c7be5d8
Reviewed-on: http://gerrit.causes.com/36492
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Change wording of SpaceBeforeBrace message

Use "should" instead of "must", which follows our convention for other
lints.

Change-Id: I187db851581ed4f2c1b76c98c7f4a73bb35308d6
Reviewed-on: http://gerrit.causes.com/36493
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>