FEATURE: Output does not create directories

[Chowarmaan]

When specifying the output file, the tsviz will not create the directory tree if it does not exist, and an actual output file is not generated. Ideally, the directory should be created. At the very least, an error that the program cannot create the image should be returned to the user.

tsviz -r src/ path/to/missing/dir/Graph.png