Percentate as an attribute value causes syntax error

[SomMeri]

Sample input:

[width=10%] {
  dimension: percent; 
}

Error:

SyntaxError: expected ']' got '%' in <...>\node.js-1.5.0-beta-b3\test.less on line 16, column 10:
15
16 [width=10%] {
17   dimension: percent;

Expected behavior: output should be the same as input.

Note 1: other number types (mm, cm, deg) work correctly. Only percentage seems to have problem.
Note 2: I think it is a bug, so I labeled it as one.

Tested with 1.5.0-beta-b3.

[lukeapage]

fix merged in