Added wrapper to allow script to run without activating application

Script no longer activates Things unless configured to do so. Output
can now go to both disk and screen by configuring toggleShowOutput.
When the application is not running and not activated by the script,
the script will attempt to read previous output from disk and print
this to screen.
Updated README, added .gitignore

Updated README, added generic OS X .gitignore
Added option for prioritisation of overdue tasks

Tasks that are overdue can be listed at the top of each individual
section, and a configurable string added to each line. Also corrected a
bug at the end of the script. Comment lined now start with a double
dash instead of a hash.
Merge pull request #2 from robdejonge/master

Added wrapper to allow script to run without activating Things.