Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/ansi-regex/index.js

@@ -0,0 +1,14 @@
+'use strict';
+
+module.exports = options => {
+	options = Object.assign({
+		onlyFirst: false
+	}, options);
+
+	const pattern = [
+		'[\\u001B\\u009B][[\\]()#;?]*(?:(?:(?:[a-zA-Z\\d]*(?:;[-a-zA-Z\\d\\/#&.:=?%@~_]*)*)?\\u0007)',
+		'(?:(?:\\d{1,4}(?:;\\d{0,4})*)?[\\dA-PR-TZcf-ntqry=><~]))'
+	].join('|');
+
+	return new RegExp(pattern, options.onlyFirst ? undefined : 'g');
+};