fixed option parsing, added message parameters

[ickerwx]

The way you simply split() the rofi_options doesn't work for more complex parameters that contain spaces, but shlex.split() fixes that. For example, you can't use --rofi-options="-mesg 'This is some text'", but you can with my fix. Additionally, I wanted to display text in the rofi message UI element. Using --search-mesg "foo bar" will result in -mesg "foo bar" being passed to the search rofi call, same with the --result-mesg parameter for the result rofi call.

[andersju]

Looks good - thanks for the fix and the feature!