update elements and fix some bugs

lib/src/prism/tests/languages/stylus/keyword_feature.test

+for i in 1..5
+if a == 3
+z-index: 1 unless @z-index;
+return pair[1] if pair[0] == key for pair in hash
+
+----------------------------------------------------
+
+[
+        ["statement", [
+                ["keyword", "for"],
+                " i ",
+                ["operator", "in"],
+                ["number", "1"],
+                ["operator", ".."],
+                ["number", "5"]
+        ]],
+        ["statement", [
+                ["keyword", "if"],
+                " a ",
+                ["operator", "=="],
+                ["number", "3"]
+        ]],
+        ["property-declaration", [
+                ["property", ["z-index"]],
+                ["punctuation", ":"],
+                ["number", "1"],
+                ["keyword", "unless"],
+                ["keyword", "@z-index"],
+                ["punctuation", ";"]
+        ]],
+        ["statement", [
+                ["keyword", "return"], " pair",
+                ["punctuation", "["], ["number", "1"], ["punctuation", "]"],
+                ["keyword", "if"], " pair",
+                ["punctuation", "["], ["number", "0"], ["punctuation", "]"],
+                ["operator", "=="], " key ",
+                ["keyword", "for"], " pair ",
+                ["operator", "in"], " hash"
+        ]]
+]
+
+----------------------------------------------------
+
+Checks for statements and keywords.