file, if it exists, and prints a delta time
from the last time this program updated the file
and appends the time information to the file.

Note: file can be /dev/null or ""

If the file does not exist it creates it and
write the current time information.
You can add optional comments that will be added
to the end of the line.

tymer can be called as a function:
from tymer import tymer
tymer()                          prints to stdout
tymer("file")                    prints to file
tymer(["file","comments"]