Added file level -F fsevent_watch option, debug output option

Trigger on file paths was not firing correctly, which was down to the fsevent_watch command not being passed the -F option. Added this as an option for trigger. For debugging purposes, I thought it would be useful to echo all variables.
minor spelling mistake in show_usage
Updated markdown to include information about the options and strikethrough todos
Added homebrew formula to install via homebrew
Merge pull request #2 from september28/master

Merge from september28/master

Added file level -F fsevent_watch option, debug output option 
Added home-brew formula to install via homebrew