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/function-bind/.editorconfig

@@ -0,0 +1,20 @@
+root = true
+
+[*]
+indent_style = tab
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+max_line_length = 120
+
+[CHANGELOG.md]
+indent_style = space
+indent_size = 2
+
+[*.json]
+max_line_length = off
+
+[Makefile]
+max_line_length = off