SystemHelper: find_files now accepts a :file_type options, which can narrow the search to files or directories only.
spotlight.rb: only files are now searched by default; the option '--include-directories' allows directories to be included.
SystemHelper: added open_browser().
start_rails: it now uses the new SystemHelper#open_browser, which is platform-independent. Also removed the obsolete constant POLLING_TIME.
spotlight.rb: the execution of the files is now asynchronous.