add MarshalJSON and UnmarshalJSON to BitArray (#200)

See CHANGELOG

common/string_test.go

@@ -49,3 +49,18 @@ func TestSplitAndTrim(t *testing.T) {
 		assert.Equal(t, tc.expected, SplitAndTrim(tc.s, tc.sep, tc.cutset), "%s", tc.s)
 	}
 }
+
+func TestIsASCIIText(t *testing.T) {
+	notASCIIText := []string{
+		"", "\xC2", "\xC2\xA2", "\xFF", "\x80", "\xF0", "\n", "\t",
+	}
+	for _, v := range notASCIIText {
+		assert.False(t, IsHex(v), "%q is not ascii-text", v)
+	}
+	asciiText := []string{
+		" ", ".", "x", "$", "_", "abcdefg;", "-", "0x00", "0", "123",
+	}
+	for _, v := range asciiText {
+		assert.True(t, IsASCIIText(v), "%q is ascii-text", v)
+	}
+}