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/lodash/_baseSome.js

@@ -0,0 +1,22 @@
+var baseEach = require('./_baseEach');
+
+/**
+ * The base implementation of `_.some` without support for iteratee shorthands.
+ *
+ * @private
+ * @param {Array|Object} collection The collection to iterate over.
+ * @param {Function} predicate The function invoked per iteration.
+ * @returns {boolean} Returns `true` if any element passes the predicate check,
+ *  else `false`.
+ */
+function baseSome(collection, predicate) {
+  var result;
+
+  baseEach(collection, function(value, index, collection) {
+    result = predicate(value, index, collection);
+    return !result;
+  });
+  return !!result;
+}
+
+module.exports = baseSome;