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/qs/.editorconfig

@@ -0,0 +1,30 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+max_line_length = 140
+
+[test/*]
+max_line_length = off
+
+[*.md]
+max_line_length = off
+
+[*.json]
+max_line_length = off
+
+[Makefile]
+max_line_length = off
+
+[CHANGELOG.md]
+indent_style = space
+indent_size = 2
+
+[LICENSE]
+indent_size = 2
+max_line_length = off