Make line-numbers styles more specific

The padding added to `pre.line-numbers` in the line-number's CSS is
overwritten by the theme's CSS if the theme is loaded second. This
ensures the CSS can come in any order without specificity issues.

plugins/line-numbers/prism-line-numbers.css

@@ -1,12 +1,12 @@
-pre.line-numbers {
+pre[class*="language-"].line-numbers {
 	position: relative;
 	padding-left: 3.8em;
 	counter-reset: linenumber;
 }
 
-pre.line-numbers > code {
+pre[class*="language-"].line-numbers > code {
 	position: relative;
-    white-space: inherit;
+	white-space: inherit;
 }
 
 .line-numbers .line-numbers-rows {
@@ -38,4 +38,4 @@ pre.line-numbers > code {
 			display: block;
 			padding-right: 0.8em;
 			text-align: right;
-		}
+		}