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/yargs/locales/pirate.json

@@ -0,0 +1,13 @@
+{
+  "Commands:": "Choose yer command:",
+  "Options:": "Options for me hearties!",
+  "Examples:": "Ex. marks the spot:",
+  "required": "requi-yar-ed",
+  "Missing required argument: %s": {
+    "one": "Ye be havin' to set the followin' argument land lubber: %s",
+    "other": "Ye be havin' to set the followin' arguments land lubber: %s"
+  },
+  "Show help": "Parlay this here code of conduct",
+  "Show version number": "'Tis the version ye be askin' fer",
+  "Arguments %s and %s are mutually exclusive" : "Yon scurvy dogs %s and %s be as bad as rum and a prudish wench"
+}