Fix braced syntax

Allow nested rules to be specified in a single line when braces
are used
Refactor parser grammar

Reuse postdent in outdent
Allow semicolon to follow @import
Refactor parser grammar

Remove singleLineRules and singleLineProperties
Allow "} @else {"
Add single line @if and @else unit test
Allow semicolon to follow @extend
Add unit test for braced @if and @else