* Add command line parameter to specify log file
I had the logs of my debug helix mixed in with the logs from the
production helix.
Add a `--log` command line argument to redirect any logs to other
files, making my debugging easier :-)
* Update completion files with `--log` argument
* adds --vsplit and --hsplit arguments
* moved comment
* fixed lint (third time's a charm)
* changed vsplit and hsplit from two separate bools to type Option<Layout>, and some cleanup
