fix(regions): Fix applying regions class

[netil]

Issue

#3611

Details

update ".bb-region rect" rule to not interfere applying regions.class rule

/* before 3.10 */
.bb-region {
	fill: steelblue;
	fill-opacity: .1;
}

/* 
3.10+
previous css rule updated as below, because "fill-opacity" property is affect all descendant elements(like text).
*/
.bb-region {
	rect {
		fill: steelblue;
		fill-opacity: .1;
	}
}

will be updated as

.bb-region {
       fill: steelblue;

       /* it still remains possibility to not take effect, when regions.class='some' contains fill-opacity property */
       /* in that case, needs consider specifity ex.: .some rect { fill:red; fill-opacity: 0.5 } */
	rect {
		fill-opacity: .1;
	}
}

[coveralls]

coverage: 94.399%. remained the same
when pulling 8065f97 on netil:region#3611
into c277201 on naver:master.