Invalidate cache when any option is changed

This was suggested in the original no-container pull request, but I didn't
understand the reason for it. After experimentation I now see that Sass doesn't
break its cache when options that affect file contents are changed. Bummer. Just
to be safe let's break cache when any option is changed -- if people complain we
can remove some that certainly don't affect output files like our own `verbose`.

lib/utils.js

@@ -10,8 +10,8 @@ exports.emitErr = function (stream, err) {
 };
 
 // Create unique temporary directory path per task using cwd, options, sources,
-// and all matched files. Sourcemap option switching does not break Sass cache
-// so we do it ourselves. Possibly a bug: https://github.com/sass/sass/issues/1830
+// and all matched files. Switching options does not break Sass cache so we do
+// it ourselves. Possibly a bug: https://github.com/sass/sass/issues/1830
 exports.createIntermediatePath = function (sources, matches, options) {
 	return path.join(
 		options.tempDir,
@@ -20,7 +20,7 @@ exports.createIntermediatePath = function (sources, matches, options) {
 			process.cwd() +
 			JSON.stringify(sources) +
 			JSON.stringify(matches) +
-			options.sourcemap
+			JSON.stringify(options)
 		)
 	);
 };